Context coding for matrix-based intra prediction

ABSTRACT

Devices, systems and methods for digital video coding, which includes matrix-based intra prediction methods for video coding, are described. In a representative aspect, a method for video processing includes encoding a current video block of a video using a matrix intra prediction (MIP) mode in which a prediction block of the current video block is determined by performing, on previously coded samples of the video, a boundary downsampling operation, followed by a matrix vector multiplication operation, and selectively followed by an upsampling operation; and adding, to a coded representation of the current video block, a syntax element indicative of applicability of the MIP mode to the current video block using arithmetic coding in which a context for the syntax element is derived based on a rule.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Application No. 17/479,338filed on Sep. 20, 2021, which is a continuation of International PatentApplication No. PCT/CN2020/088583, filed on May 5, 2020, which claimsthe priority to and benefits of International Patent Application No.PCT/CN2019/085399 filed on May 1, 2019. All the aforementioned patentapplications are hereby incorporated by reference in their entireties.

TECHNICAL FIELD

This patent document relates to video coding techniques, devices andsystems.

BACKGROUND

In spite of the advances in video compression, digital video stillaccounts for the largest bandwidth use on the internet and other digitalcommunication networks. As the number of connected user devices capableof receiving and displaying video increases, it is expected that thebandwidth demand for digital video usage will continue to grow.

SUMMARY

Devices, systems and methods related to digital video coding, andspecifically, matrix-based intra prediction methods for video coding aredescribed. The described methods may be applied to both the existingvideo coding standards (e.g., High Efficiency Video Coding (HEVC)) andfuture video coding standards (e.g., Versatile Video Coding (VVC)) orcodecs.

A first example method for video processing includes performing aconversion between a current video block of a video and a bitstreamrepresentation of the current video block using a matrix based intraprediction (MIP) mode in which a prediction block of the current videoblock is determined by performing, on reference boundary samples locatedto a left of the current video block and located to a top of the currentvideo block, a boundary downsampling operation, followed by a matrixvector multiplication operation, and selectively followed by anupsampling operation, where instead of reduced boundary samplescalculated from the reference boundary samples of the current videoblock in the boundary downsampling operation, the reference boundarysamples are directly used for a prediction process in the upsamplingoperation.

A second example method for video processing includes performing, duringa conversion between a current video block of a video and a bitstreamrepresentation of the current video block, at least two filtering stageson samples of the current video block in an upsampling operationassociated with a matrix based intra prediction (MIP) mode in which aprediction block of the current video block is determined by performing,on previously coded samples of the video, a boundary downsamplingoperation, followed by a matrix vector multiplication operation, andselectively followed by the upsampling operation, where a firstprecision of the samples in a first filtering stage of the at least twofiltering stages is different from a second precision of the samples ina second filtering stage of the at least two filtering stages; andperforming the conversion between the current video block and thebitstream representation of the current video block.

A third example video encoding method includes encoding a current videoblock of a video using a matrix intra prediction (MIP) mode in which aprediction block of the current video block is determined by performing,on previously coded samples of the video, a boundary downsamplingoperation, followed by a matrix vector multiplication operation, andselectively followed by an upsampling operation; and adding, to a codedrepresentation of the current video block, a syntax element indicativeof applicability of the MIP mode to the current video block usingarithmetic coding in which a context for the syntax element is derivedbased on a rule.

A fourth example video decoding method includes parsing a codedrepresentation of a video comprising a current video block for a syntaxelement indicating whether the current video block is coded using amatrix intra prediction (MIP) mode, wherein the syntax element is codedusing arithmetic coding in which a context for the syntax element isderived based on a rule; and decoding the coded representation of thecurrent video block to generate a decoded current video block, whereinin a case that the current video block is coded using the MIP mode, thedecoding includes determining a prediction block of the current videoblock by performing, on previously coded samples of the video, aboundary downsampling operation, followed by a matrix vectormultiplication operation, and selectively followed by an upsamplingoperation.

In one representative aspect, the disclosed technology may be used toprovide a method for video processing. This exemplary method includesdetermining that a current video block is coded using an affine linearweighted intra prediction (ALWIP) mode, constructing, based on thedetermining, at least a portion of a most probable mode (MPM) list forthe ALWIP mode based on an at least a portion of an MPM list for anon-ALWIP intra mode, and performing, based on the MPM list for theALWIP mode, a conversion between the current video block and a bitstreamrepresentation of the current video block.

In another representative aspect, the disclosed technology may be usedto provide a method for video processing. This exemplary method includesdetermining that a luma component of a current video block is codedusing an affine linear weighted intra prediction (ALWIP) mode,inferring, based on the determining, a chroma intra mode, andperforming, based on the chroma intra mode, a conversion between thecurrent video block and a bitstream representation of the current videoblock.

In yet another representative aspect, the disclosed technology may beused to provide a method for video processing. This exemplary methodincludes determining that a current video block is coded using an affinelinear weighted intra prediction (ALWIP) mode, and performing, based onthe determining, a conversion between the current video block and abitstream representation of the current video block.

In yet another representative aspect, the disclosed technology may beused to provide a method for video processing. This exemplary methodincludes determining that a current video block is coded using a codingmode different from an affine linear weighted intra prediction (ALWIP)mode, and performing, based on the determining, a conversion between thecurrent video block and a bitstream representation of the current videoblock.

In yet another representative aspect, the disclosed technology may beused to provide a method for video processing. This exemplary methodincludes generating, for a current video block, a first prediction usingan affine linear weighted intra prediction (ALWIP) mode, generating,based on the first prediction, a second prediction using positiondependent intra prediction combination (PDPC), and performing, based onthe second prediction, a conversion between the current video block anda bitstream representation of the current video block.

In yet another representative aspect, the disclosed technology may beused to provide a method for video processing. This exemplary methodincludes determining that a current video block is coded using an affinelinear weighted intra prediction (ALWIP) mode, predicting, based on theALWIP mode, a plurality of sub-blocks of the current video block, andperforming, based on the predicting, a conversion between the currentvideo block and a bitstream representation of the current video block.

In yet another representative aspect, a method of video processing isdisclosed. The method includes determining, based on a rule for acurrent video block, a context of a flag indicative of use of affinelinear weighted intra prediction (ALWIP) mode during a conversionbetween the current video block and a bitstream representation of thecurrent video block, predicting, based on the ALWIP mode, a plurality ofsub-blocks of the current video block and performing, based on thepredicting, the conversion between the current video block and abitstream representation of the current video block.

In yet another representative aspect, a method of video processing isdisclosed. The method includes determining that a current video block iscoded using an affine linear weighted intra prediction (ALWIP) mode, andperforming, during a conversion between the current video block and abitstream representation of the current video block, at least twofiltering stages on samples of the current video block in an upsamplingprocess associated with the ALWIP mode, wherein a first precision of thesamples in a first filtering stage of the at least two filtering stagesis different from a second precision of the samples in a secondfiltering stage of the at least two filtering stages.

In yet another representative aspect, the above-described method isembodied in the form of processor-executable code and stored in acomputer-readable program medium.

In yet another representative aspect, a device that is configured oroperable to perform the above-described method is disclosed. The devicemay include a processor that is programmed to implement this method.

In yet another representative aspect, a video decoder apparatus mayimplement a method as described herein.

The above and other aspects and features of the disclosed technology aredescribed in greater detail in the drawings, the description and theclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of 33 intra prediction directions.

FIG. 2 shows an example of 67 intra prediction modes.

FIG. 3 shows an example of locations of samples used for the derivationof the weights of the linear model.

FIG. 4 shows an example of four reference lines neighboring a predictionblock.

FIG. 5A and FIG. 5B show examples of sub-partitions depending on blocksize.

FIG. 6 shows an example of ALWIP for 4×4 blocks.

FIG. 7 shows an example of ALWIP for 8×8 blocks.

FIG. 8 shows an example of ALWIP for 8×4 blocks.

FIG. 9 shows an example of ALWIP for 16×16 blocks.

FIG. 10 shows an example of neighboring blocks using in MPM listconstruction.

FIG. 11 shows a flowchart of an example method for matrix-based intraprediction, in accordance with the disclosed technology.

FIG. 12 shows a flowchart of another example method for matrix-basedintra prediction, in accordance with the disclosed technology.

FIG. 13 shows a flowchart of yet another example method for matrix-basedintra prediction, in accordance with the disclosed technology.

FIG. 14 shows a flowchart of yet another example method for matrix-basedintra prediction, in accordance with the disclosed technology.

FIG. 15 is a block diagram of an example of a hardware platform forimplementing a visual media decoding or a visual media encodingtechnique described in the present document.

FIG. 16 shows an example of neighboring blocks.

FIG. 17 is a block diagram that illustrates an example video codingsystem that may utilize the techniques of this disclosure.

FIG. 18 is a block diagram illustrating an example of video encoder.

FIG. 19 is a block diagram illustrating an example of video decoder.

FIG. 20 is a block diagram showing an example video processing system inwhich various techniques disclosed herein may be implemented.

FIGS. 21-24 describe example methods for matrix-based intra prediction,in accordance with the disclosed technology.

DETAILED DESCRIPTION

Due to the increasing demand of higher resolution video, video codingmethods and techniques are ubiquitous in modern technology. Video codecstypically include an electronic circuit or software that compresses ordecompresses digital video, and are continually being improved toprovide higher coding efficiency. A video codec converts uncompressedvideo to a compressed format or vice versa. There are complexrelationships between the video quality, the amount of data used torepresent the video (determined by the bit rate), the complexity of theencoding and decoding algorithms, sensitivity to data losses and errors,ease of editing, random access, and end-to-end delay (latency). Thecompressed format usually conforms to a standard video compressionspecification, e.g., the High Efficiency Video Coding (HEVC) standard(also known as H.265 or Motion Picture Experts Group (MPEG)-H Part 2),the Versatile Video Coding (VVC) standard to be finalized, or othercurrent and/or future video coding standards.

Embodiments of the disclosed technology may be applied to existing videocoding standards (e.g., HEVC, H.265) and future standards to improveruntime performance. Section headings are used in the present documentto improve readability of the description and do not in any way limitthe discussion or the embodiments (and/or implementations) to therespective sections only.

1. A Brief Review on HEVC 1.1 Intra Prediction in HEVC/H.265

Intra prediction involves producing samples for a given TB (transformblock) using samples previously reconstructed in the considered colorchannel. The intra prediction mode is separately signaled for the lumaand chroma channels, with the chroma channel intra prediction modeoptionally dependent on the luma channel intra prediction mode via the‘DM_CHROMA’ mode. Although the intra prediction mode is signaled at thePB (prediction block) level, the intra prediction process is applied atthe TB level, in accordance with the residual quad-tree hierarchy forthe CU (coding unit), thereby allowing the coding of one TB to have aneffect on the coding of the next TB within the CU, and thereforereducing the distance to the samples used as reference values.

HEVC includes 35 intra prediction modes - a direct current (DC) mode, aplanar mode and 33 directional, or ‘angular’ intra prediction modes. The33 angular intra prediction modes are illustrated in FIG. 1 .

For PBs associated with chroma color channels, the intra prediction modeis specified as either planar, DC, horizontal, vertical, ‘DM_CHROMA’mode or sometimes diagonal mode ‘34’.

Note for chroma formats 4:2:2 and 4:2:0, the chroma PB may overlap twoor four (respectively) luma PBs; in this case the luma direction forDM_CHROMA is taken from the top left of these luma PBs.

The DM_CHROMA mode indicates that the intra prediction mode of the lumacolor channel PB is applied to the chroma color channel PBs. Since thisis relatively common, the most-probable-mode coding scheme of theintra_chroma_pred_mode is biased in favor of this mode being selected.

2 Examples of Intra Prediction in VVC 2.1 Intra Mode Coding with 67Intra Prediction Modes

To capture the arbitrary edge directions presented in natural video, thenumber of directional intra modes is extended from 33, as used in HEVC,to 65. The additional directional modes are depicted as dotted arrows inFIG. 2 , and the planar and DC modes remain the same. These denserdirectional intra prediction modes apply for all block sizes and forboth luma and chroma intra predictions.

2.2 Examples of the Cross-Component Linear Model (CCLM)

In some embodiments, and to reduce the cross-component redundancy, across-component linear model (CCLM) prediction mode (also referred to asLM), is used in the Joint Exploration Model (JEM), for which the chromasamples are predicted based on the reconstructed luma samples of thesame CU by using a linear model as follows:

pred_(C)(i, j) = α ⋅ rec_(L)^(′)(i, j) + β

Here, pred_(c)(i,j) represents the predicted chroma samples in a CU andrec_(L)'(i,j) represents the downsampled reconstructed luma samples ofthe same CU. Linear model parameter α and β are derived from therelation between luma values and chroma values from two samples, whichare luma sample with minimum sample value and with maximum sample insidethe set of downsampled neighboring luma samples, and their correspondingchroma samples. FIG. 3 shows an example of the location of the left andabove samples and the sample of the current block involved in the CCLMmode.

This parameter computation is performed as part of the decoding process,and is not just as an encoder search operation. As a result, no syntaxis used to convey the α and β values to the decoder.

For chroma intra mode coding, a total of 8 intra modes are allowed forchroma intra mode coding. Those modes include five traditional intramodes and three cross-component linear model modes (CCLM, LM_A, andLM_L). Chroma mode coding directly depends on the intra prediction modeof the corresponding luma block. Since separate block partitioningstructure for luma and chroma components is enabled in I slices, onechroma block may correspond to multiple luma blocks. Therefore, forChroma derived-mode (DM) mode, the intra prediction mode of thecorresponding luma block covering the center position of the currentchroma block is directly inherited.

2.3 Multiple Reference Line (MRL) Intra Prediction

Multiple reference line (MRL) intra prediction uses more reference linesfor intra prediction. In FIG. 4 , an example of 4 reference lines isdepicted, where the samples of segments A and F are not fetched fromreconstructed neighboring samples but padded with the closest samplesfrom Segment B and E, respectively. HEVC intra-picture prediction usesthe nearest reference line (i.e., reference line 0). In MRL, 2additional lines (reference line 1 and reference line 3) are used. Theindex of selected reference line (mrl_idx) is signalled and used togenerate intra predictor. For reference line idx, which is greater than0, only include additional reference line modes in MPM list and onlysignal mpm index without remaining mode.

2.4 Intra Sub-Partitions (ISP)

The Intra Sub-Partitions (ISP) tool divides luma intra-predicted blocksvertically or horizontally into 2 or 4 sub-partitions depending on theblock size. For example, minimum block size for ISP is 4×8 (or 8×4). Ifblock size is greater than 4×8 (or 8×4) then the corresponding block isdivided by 4 sub-partitions. FIG. 5 shows examples of the twopossibilities. All sub-partitions fulfill the condition of having atleast 16 samples.

For each sub-partition, reconstructed samples are obtained by adding theresidual signal to the prediction signal. Here, a residual signal isgenerated by the processes such as entropy decoding, inversequantization and inverse transform. Therefore, the reconstructed samplevalues of each sub-partition are available to generate the prediction ofthe next sub-partition, and each sub-partition is processed repeatedly.In addition, the first sub-partition to be processed is the onecontaining the top-left sample of the CU and then continuing downwards(horizontal split) or rightwards (vertical split). As a result,reference samples used to generate the sub-partitions prediction signalsare only located at the left and above sides of the lines. Allsub-partitions share the same intra mode.

2.5 Affine Linear Weighted Intra Prediction (ALWIP or Matrix-Based IntraPrediction)

Affine linear weighted intra prediction (ALWIP, a.k.a. Matrix basedintra prediction (MIP)) is proposed in Joint Video Experts Team(JVET)-N0217.

In JVET-N0217, two tests are conducted. In test 1, ALWIP is designedwith a memory restriction of eight Kilobytes (8 KB) and at most 4multiplications per sample. Test 2 is similar to test 1, but furthersimplifies the design in terms of memory requirement and modelarchitecture.

Single set of matrices and offset vectors for all block shapes.

Reduction of number of modes to 19 for all block shapes.

Reduction of memory requirement to 5760 10-bit values, that is 7.20Kilobytes.

Linear interpolation of predicted samples is carried out in a singlestep per direction replacing iterative interpolation as in the firsttest.

2.5.1 Test 1 of JVET-N0217

For predicting the samples of a rectangular block of width W and heightH, affine linear weighted intra prediction (ALWIP) takes one line of Hreconstructed neighboring boundary samples left of the block and oneline of W reconstructed neighboring boundary samples above the block asinput. If the reconstructed samples are unavailable, they are generatedas it is done in the conventional intra prediction.

The generation of the prediction signal is based on the following threesteps:

Out of the boundary samples, four samples in the case of W = H = 4 andeight samples in all other cases are extracted by averaging.

A matrix vector multiplication, followed by addition of an offset, iscarried out with the averaged samples as an input. The result is areduced prediction signal on a subsampled set of samples in the originalblock.

The prediction signal at the remaining positions is generated from theprediction signal on the subsampled set by linear interpolation which isa single step linear interpolation in each direction.

The matrices and offset vectors needed to generate the prediction signalare taken from three sets S₀, S₁, S₂ of matrices. The set S₀ consists of18 matrices

A₀^(i), i ∈ {0, ..., 17}

each of which has 16 rows and 4 columns and 18 offset vectors

b₀^(i), i ∈ {0, ..., 17}

each of size 16. Matrices and offset vectors of that set are used forblocks of size 4 × 4. The set S₁ consists of 10 matrices

A₁^(i)l ∈ {0, ..., 9}

,, each of which has 16 rows and 8 columns and 10 offset vectors

b₁^(i), i ∈ {0, ..., 9}

, i ∈ {0, ..., 9} each of size 16. Matrices and offset vectors of thatset are used for blocks of sizes 4 × 8, 8 × 4 and 8 × 8. Finally, theset S₂ consists of 6 matrices

A₂^(i), i ∈ {0, ..., 5}

, each of which has 64 rows and 8 columns and of 6 offset vectors

b₂^(i), i ∈ {0, ..., 5}

of size 64. Matrices and offset vectors of that set or parts of thesematrices and offset vectors are used for all other block-shapes.

The total number of multiplications needed in the computation of thematrix vector product is always smaller than or equal to 4 × W × H . Inother words, at most four multiplications per sample are required forthe ALWIP modes.

2.5.2 Averaging of the Boundary

In a first step, the input boundaries bdry^(top) and bdry^(left) arereduced to smaller boundaries

bdry_(red)^(top)

and

bdry_(red)^(left)

. Here,

bdry_(red)^(top)

and

bdry_(red)^(left)

bdryredt both consists of 2 samples in the case of a 4 × 4-block andboth consist of 4 samples in all other cases.

In the case of a 4 × 4-block, for 0 ≤ i < 2, one defines:

$bdry_{red}^{top}\lbrack i\rbrack = \left( {\left( {\sum\limits_{j = 0}^{1}{bdry^{top}\left\lbrack {i \cdot 2 + j} \right\rbrack}} \right) + 1} \right) \gg 1$

and defines

bdry_(red)^(left)

analogously.

Otherwise, if the block-width W is given as W = 4 · 2^(k), for 0 ≤ i <4, one defines:

$bdry_{red}^{top}\lbrack i\rbrack = \left( {\left( {\sum\limits_{j = 0}^{2^{k} - 1}{bdry^{top}\left\lbrack {i \cdot 2^{k} + j} \right\rbrack}} \right) + \left( {1 \ll \left( {k - 1} \right)} \right)} \right) \gg k$

and defines

bdry_(red)^(left)

analogously.

The two reduced boundaries

bdry_(red)^(top)

and

bdry_(red)^(left)

are concatenated to a reduced boundary vector bdry_(red) which is thusof size four for blocks of shape 4 × 4 and of size eight for blocks ofall other shapes. If mode refers to the ALWIP-mode, this concatenationis defined as follows:

$bdry_{red} = \left\{ \begin{array}{ll}\left\lbrack {bdry_{red}^{top},bdry_{red}^{left}} \right\rbrack & {\text{for}W = H = 4\text{and}mode < 18} \\\left\lbrack {bdry_{red}^{left},bdry_{red}^{top}} \right\rbrack & {\text{for}W = H = 4\text{and}mode \geq 18} \\\left\lbrack {bdry_{red}^{top},bdry_{red}^{left}} \right\rbrack & {\text{for}\mspace{6mu}\max\left( {W,H} \right) = 8\text{and}mode < 10} \\\left\lbrack {bdry_{red}^{left},bdry_{red}^{top}} \right\rbrack & {\text{for}\mspace{6mu}\max\left( {W,H} \right) = 8\text{and}mode \geq 10} \\\left\lbrack {bdry_{red}^{top},bdry_{red}^{left}} \right\rbrack & {\text{for}\mspace{6mu}\max\left( {W,H} \right) > 8\text{and}mode < 6} \\\left\lbrack {bdry_{red}^{left},bdry_{red}^{top}} \right\rbrack & {\text{for}\mspace{6mu}\max\left( {W,H} \right) > 8\text{and}mode \geq 6.}\end{array} \right)$

Finally, for the interpolation of the subsampled prediction signal, onlarge blocks a second version of the averaged boundary is needed.Namely, if min(W, H) > 8 and W ≥ H, one writes W= 8 * 2^(l), and, for 0≤ i < 8, defines:

$bdry_{redII}^{top}\lbrack i\rbrack = \left( {\left( {\sum\limits_{j = 0}^{2^{l} - 1}{bdry^{top}\left\lbrack {i \cdot 2^{l} + j} \right\rbrack}} \right) + \left( {1 \ll \left( {l - 1} \right)} \right)} \right) \gg l.$

If min(W, H) > 8 and H > W, one defines

bdry_(redII)^(left)

analogously.

2.5.3 Generation of the Reduced Prediction Signal by Matrix VectorMultiplication

Out of the reduced input vector bdry_(red) one generates a reducedprediction signal pred_(red). The latter signal is a signal on thedownsampled block of width W_(red) and height H_(red). Here, W_(red) andH_(red) are defined as:

$W_{red} = \left\{ \begin{matrix}4 & {\text{for}\max\left( {W,H} \right) \leq 8} \\{\min\left( {W,8} \right)} & {\text{for}\max\left( {W,H} \right) > 8}\end{matrix} \right)$

$H_{red} = \left\{ \begin{matrix}4 & {\text{for}\max\left( {W,H} \right) \leq 8} \\{\min\left( {H,8} \right)} & {\text{for}\max\left( {W,H} \right) > 8}\end{matrix} \right)$

The reduced prediction signal pred_(red) is computed by calculating amatrix vector product and adding an offset:

pred_(red) = A ⋅ bdry_(red) + b

Here, A is a matrix that has W_(red) • H_(red) rows and 4 columns if W =H = 4 and 8 columns in all other cases. bis a vector of size W_(red) •H_(red) .

The matrix A and the vector b are taken from one of the sets S₀, S₁, S₂as follows. One defines an index idx = idx(W, H) as follows:

$idx\left( {W,H} \right) = \left\{ \begin{array}{ll}0 & {\text{for W} = \text{H} = 4} \\1 & {\text{for}\max\left( {W,H} \right) = 8} \\2 & {\text{for}\max\left( {W,H} \right) > 8.}\end{array} \right)$

Moreover, one puts m as follows:

$m = \left\{ \begin{array}{ll}{mode} & {\text{for}W = H = 4\text{and}mode < 18} \\{mode - 17} & {\text{for}W = H = 4\text{and}mode \geq 18} \\{mode} & {\text{for max}\left( {W,H} \right) = 8\text{and}mode < 10} \\{mode - 9} & {\text{for max}\left( {W,H} \right) = 8\text{and}mode \geq 10} \\{mode} & {\text{for max}\left( {W,H} \right) > 8\text{and}mode < 6} \\{mode - 5} & {\text{for max}\left( {W,H} \right) > 8\text{and}mode \geq 6.}\end{array} \right)$

Then, if idx ≤ 1 or idx = 2 and min(W, H) > 4, one puts

A = A_(idx)^(m)

and

b = b_(idx)^(m)

. In the case that idx = 2 and min(W, H) = 4, one lets A be the matrixthat arises by leaving out every row of

A_(idx)^(m)

that, in the case W = 4, corresponds to an odd x-coordinate in thedownsampled block, or, in the case H = 4, corresponds to an oddy-coordinate in the downsampled block.

Finally, the reduced prediction signal is replaced by its transpose inthe following cases:

W = H = 4andmode ≥ 18

max (W, H) = 8andmode ≥ 10

max (W, H) > 8andmode ≥ 6

The number of multiplications required for calculation of pred_(red) is4 in the case of W = H = 4 since in this case A has 4 columns and 16rows. In all other cases, A has 8 columns and W_(red) • H_(red) rows andone immediately verifies that in these cases 8 •W_(red) • H_(red) ≤ 4 •W • H multiplications are required, i.e. also in these cases, at most 4multiplications per sample are needed to compute pred_(red).

2.5.4 Illustration of the Entire ALWIP Process

The entire process of averaging, matrix vector multiplication and linearinterpolation is illustrated for different shapes in FIGS. 6-9 . Note,that the remaining shapes are treated as in one of the depicted cases.

1. Given a 4 × 4 block, ALWIP takes two averages along each axis of theboundary. The resulting four input samples enter the matrix vectormultiplication. The matrices are taken from the set S₀. After adding anoffset, this yields the 16 final prediction samples. Linearinterpolation is not necessary for generating the prediction signal.Thus, a total of (4 • 16)/(4 • 4) = 4 multiplications per sample areperformed.

2. Given an 8 × 8 block, ALWIP takes four averages along each axis ofthe boundary. The resulting eight input samples enter the matrix vectormultiplication. The matrices are taken from the set S₁. This yields 16samples on the odd positions of the prediction block. Thus, a total of(8 • 16)/(8 • 8) = 2 multiplications per sample are performed. Afteradding an offset, these samples are interpolated vertically by using thereduced top boundary. Horizontal interpolation follows by using theoriginal left boundary.

3. Given an 8 × 4 block, ALWIP takes four averages along the horizontalaxis of the boundary and the four original boundary values on the leftboundary. The resulting eight input samples enter the matrix vectormultiplication. The matrices are taken from the set S₁. This yields 16samples on the odd horizontal and each vertical positions of theprediction block. Thus, a total of (8 • 16)/(8 • 4) = 4 multiplicationsper sample are performed. After adding an offset, these samples areinterpolated horizontally by using the original left boundary.

4. Given a 16 × 16 block, ALWIP takes four averages along each axis ofthe boundary. The resulting eight input samples enter the matrix vectormultiplication. The matrices are taken from the set S₂. This yields 64samples on the odd positions of the prediction block. Thus, a total of(8 • 64)/(16 • 16) = 2 multiplications per sample are performed. Afteradding an offset, these samples are interpolated vertically by usingeight averages of the top boundary. Horizontal interpolation follows byusing the original left boundary. The interpolation process, in thiscase, does not add any multiplications. Therefore, totally, twomultiplications per sample are required to calculate ALWIP prediction.

For larger shapes, the procedure is essentially the same and it is easyto check that the number of multiplications per sample is less thanfour.

For W×8 blocks with W>8, only horizontal interpolation is necessary asthe samples are given at the odd horizontal and each vertical positions.

Finally for W×4 blocks with W>8, let A_kbe the matrix that arises byleaving out every row that corresponds to an odd entry along thehorizontal axis of the downsampled block. Thus, the output size is 32and again, only horizontal interpolation remains to be performed.

The transposed cases are treated accordingly.

2.5.5 Single Step Linear Interpolation

For a W × H block with max(W, H) ≥ 8, the prediction signal arises fromthe reduced prediction signal pred_(red) on W_(red) × H_(red) by linearinterpolation. Depending on the block shape, linear interpolation isdone in vertical, horizontal or both directions. If linear interpolationis to be applied in both directions, it is first applied in horizontaldirection if W < H and it is first applied in vertical direction, else.

Consider without loss of generality a W × H block with max(W, H) ≥ 8 andW ≥ H. Then, the one-dimensional linear interpolation is performed asfollows. Without loss of generality, it suffices to describe linearinterpolation in vertical direction. First, the reduced predictionsignal is extended to the top by the boundary signal. Define thevertical upsampling factor U_(ver) = H/H_(red) and write U_(ver) =2^(uver) > 1. Then, define the extended reduced prediction signal by:

$pred_{red}\lbrack x\rbrack\left\lbrack {- 1} \right\rbrack = \left\{ \begin{matrix}{bdry_{red}^{top}\lbrack x\rbrack} & {\text{for}W = 8} \\{bdry_{redII}^{top}\lbrack x\rbrack} & {\text{for}W > 8.}\end{matrix} \right)$

Then, from this extended reduced prediction signal, the verticallylinear interpolated prediction signal is generated by:

pred_(red)^(ups, ver)[x][U_(ver) ⋅ y + k]

$\begin{array}{l}{= \left( {\left( {U_{ver} - k - 1} \right) \cdot pred_{red}\lbrack x\rbrack\left\lbrack {y - 1} \right\rbrack +} \right)} \\\left( {\left( {k + 1} \right) \cdot pred_{red}\lbrack x\rbrack\lbrack y\rbrack + \frac{U_{ver}}{2}} \right)\end{array}$

 ≫ u_(ver)

for 0 ≤ × < W_(red), 0 ≤ y < H_(red) and 0 ≤ k < U_(ver).

2.5.6 Signalization of the Proposed Intra Prediction Modes

For each Coding Unit (CU) in intra mode, a flag indicating if an ALWIPmode is to be applied on the corresponding Prediction Unit (PU) or notis sent in the bitstream. The signalization of the latter index isharmonized with MRL in the same way as in JVET-M0043. If an ALWIP modeis to be applied, the index predmode of the ALWIP mode is signaled usinga MPM-list with 3 MPMs.

Here, the derivation of the MPMs is performed using the intra-modes ofthe above and the left PU as follows. There are three fixed tablesmap_angular_to_alwip_(idx), idx ∈ {0,1,2} that assign to eachconventional intra prediction mode predmode_(Angular) an ALWIP mode

predmode_(ALWIP) = map_angular_to_alwip_(idx)[predmode_(Angular)].

For each PU of width W and height H one defines an index

idx(PU) = idx(W, H) ∈ {0, 1, 2}

that indicates from which of the three sets the ALWIP-parameters are tobe taken as in Section 2.5.3.

If the above Prediction Unit PU_(above) is available, belongs to thesame coding tree unit (CTU) as the current PU and is in intra mode, ifidx(PU) = idx(PU_(above)) and if ALWIP is applied on PU_(above) withALWIP-mode

predmode_(ALWIP)^(above)

, one puts:

mode_(ALWIP)^(above) = predmode_(ALWIP)^(above)  .

If the above PU is available, belongs to the same CTU as the current PUand is in ntra mode and if a conventional intra prediction mode

predmode_(Angular)^(above)

is applied on the above PU, one puts:

mode_(ALWIP)^(above) = map_angular_to_alwip_(idx(PU_(above))) [predmode_(Angular)^(above)].

In all other cases, one puts:

mode_(ALWIP)^(above) = −1,

which means that this mode is unavailable. In the same way but withoutthe restriction that the left PU needs to belong to the same CTU as thecurrent PU, one derives a mode

mode_(ALWIP)^(left)

.

Finally, three fixed default lists list_(idx), idx ∈ {0,1,2} areprovided, each of which contains three distinct ALWIP modes. Out of thedefault list list_(idx(PU)) and the modes

mode_(ALWIP)^(above)

and

mode_(ALWIP)^(left)

, one constructs three distinct MPMs by substituting -1 by defaultvalues as well as eliminating repetitions.

The left neighboring block and above neighboring block used in the ALWIPMPM list construction is A1 and B1 as shown in FIG. 10 .

2.5.7 Adapted MPM-List Derivation for Conventional Luma and ChromaIntra-Prediction Modes

The proposed ALWIP-modes are harmonized with the MPM-based coding of theconventional intra-prediction modes as follows. The luma and chromaMPM-list derivation processes for the conventional intra-predictionmodes uses fixed tables map_alwip_to_angular_(idx), idx ∈ {0,1,2},mapping an ALWIP-mode predmode_(ALWIP) on a given PU to one of theconventional intra-prediction modes:

predmode_(Angular) = map_alwip_to_angular_(idx(PU)) [predmode_(ALWIP)]

For the luma MPM-list derivation, whenever a neighboring luma block isencountered which uses an ALWIP-mode predmode_(ALWIP), this block istreated as if it was using the conventional intra-prediction modepredmode_(Angular). For the chroma MPM-list derivation, whenever thecurrent luma block uses an LWIP-mode, the same mapping is used totranslate the ALWIP-mode to a conventional intra prediction mode.

2.5.8 Corresponding Modified Working Draft

In some embodiments, as described in this section, portions related tointra_1wip_flag, intra_lwip_mpm_flag, intra 1wip_mpm_idx andintra_lwip_mpm_remainder have been added to the working draft based onembodiments of the disclosed technology.

In some embodiments, as described in this section, the <begin> and <end>tags are used to denote additions and modifications to the working draftbased on embodiments of the disclosed technology.

Syntax Tables

Coding unit syntax

coding_unit( x0, y0, cbWidth, cbHeight, treeType ) { Descriptor  if(tile_group_type != I || sps_ibc_enabled­_flag) {   if( treeType != DUALTREE CHROMA)    cu_skip_flag[ x0 ] [ y0 ] ae(v)   if( cu_skip_flag[ x0][ y0 ] = = 0 && tile_group_type != I)    pred_mode_flag ae(v)   if( ((tile_group_type = = I && cu_skip_flag[ x0 ] [ y0 ] = =0 ) | |   (tile_group_type!= I && CuPredMode[ x0 ] [ y0 ] != MODE_INTRA) ) &&   sps_ibc_enabled_flag)    pred_mode_ibc_flag ae(v)  }  if( CuPredMode[x0 ][ y0 ] = = MODE_INTRA ) {   if( sps_pcm_enabled_flag &&   cbWidth >= MinIpcmCbSizeY && cbWidth <= MaxIpcmCbSizeY &&   cbHeight >= MinIpcmCbSizeY && cbHeight <= MaxIpcmCbSizeY )   pcm_flag[ x0 ][ y0 ] ae(v)   if( pcm_flag[ x0 ][ y0 ] ) {    while(!byte aligned( ) )     pcm_alignment_zero_bit f(1)    pcm_sample(cbWidth, cbHeight, treeType)   } else {    if( treeType = = SINGLE_TREE| | treeType = = DUAL_TREE_LUMA) {     if( Abs( Log2( cbWidth ) - Log2(cbheight ) ) <= 2 )      intra_lwip_flag[ x0 ][ y0 ] ae(v)     if(intra_lwip_flag[ x0 ][ y0 ] ) {       intra_lwip_mpm_flag[ x0 ][ y0 ]ae(v)      if( intra_lwip_mpm_flag[ x0 ][ y0 ] )      intra_lwip_mpm_idx[ x0 ][ y0 ] ae(v)      else      intra_lwip_mpm_remainder[ x0 ][ y0 ] ae(v)     } else {      if( (y0 % CtbSizeY) > 0 )       intra_luma_ref_idx[ x0 ][ y0 ] ae(v)      if(intra_luma_ref_idx[ x0][ y0 ] = = 0 &&       ( cbWidth <= MaxTbSizeY || cbHeight <= MaxTbSizeY ) &&       ( cbWidth * cbHeight > MinTbSizeY *MinTbSizeY ))       intra_subpartitions_mode_flag[ x0 ][ y0 ] ae(v)     if( intra_subpartitions_mode_flag[ x0 ][ y0 ] = = 1 &&      cbWidth <= MaxTbSizeY && cbHeight <= MaxTbSizeY )      intra_subpartitions_split_flag[ x0 ][ y0 ] ae(v)      if(intra_luma_ref_idx[ x0 ] [ [ y0 ] = = 0 &&      intra_subpartitions_mode_flag[ x0 ][ y0 ] = = 0 )      intra_luma_mpm_flag[ x0 ][ y0 ] ae(v)      if(intra_luma_mpm_flag[ x0 ][ y0 ] )       intra_luma_mpm_idx[ x0 ][ y0 ]ae(v)      else       intra_luma_mpm_remainder[ x0 ][ y0 ] ae(v)     }   }    if( treeType = = SINGLE_TREE | | treeType = = DUAL_TREE_CHROMA )    intra_chroma_pred_mode[ x0 ][ y0 ] ae(v)   }  } else if( treeType !=DUAL_TREE_CHROMA) { /* MODE_INTER or MODE IBC */   ...

Semantics

<begin>intra_lwip_flag[ x0 ][ y0 ] equal to 1 specifies that the intraprediction type for luma samples is affine linear weighted intraprediction. intra_lwip_flag[ x0 ][ y0 ] equal to 0 specifies that theintra prediction type for luma samples is not affine linear weightedintra prediction.

When intra_lwip_flag[ x0 ][ y0 ] is not present, it is inferred to beequal to 0.

The syntax elements intra_lwip_mpm_flag[ x0 ][ y0 ], intra_lwip_mpm_idx[x0 ][ y0 ] and intra_lwip_mpm_remainder [ x0 ][ y0 ] specify the affinelinear weighted intra prediction mode for luma samples. The arrayindices x0, y0 specify the location ( x0 , y0 ) of the top-left lumasample of the considered coding block relative to the top-left lumasample of the picture. When intra_lwip_mpm_flag[ x0 ][ y0 ] is equal to1, the affine linear weighted intra prediction mode is inferred from aneighboring intra-predicted coding unit according to clause 8.4.X.

When intra_lwip_mpm_flag[ x0 ][ y0 ] is not present, it is inferred tobe equal to 1.<end>

intra_subpartitions_sp)it_flag[ x0 ][ y0 ] specifies whether the intrasubpartitions split type is horizontal or vertical. Whenintra_subpartitions_split_flag[ x0 ][ y0 ] is not present, it isinferred as follows:

-   If intra_lwip_flag[ x0 ][ y0 ] is equal to 1,    intra_subpartitions_split_flag[ x0 ][ y0 ] is inferred to be equal    to 0.-   Otherwise, the following applies:    -   If cbHeight is greater than MaxTbSizeY,        intra_subpartitions_split_flag[ x0 ][ y0 ] is inferred to be        equal to 0.    -   Otherwise (cbWidth is greater than MaxTbSizeY),        intra_subpartitions_split_flag[ x0 ][ y0 ] is inferred to be        equal to 1.

Decoding Process 8.4.1 General Decoding Process for Coding Units Codedin Intra Prediction Mode

Inputs to this process are:

-   a luma location (xCb, yCb) specifying the top-left sample of the    current coding block relative to the top-left luma sample of the    current picture,-   a variable cbWidth specifying the width of the current coding block    in luma samples,-   a variable cbHeight specifying the height of the current coding    block in luma samples,-   a variable treeType specifying whether a single or a dual tree is    used and if a dual tree is used, it specifies whether the current    tree corresponds to the luma or chroma components.

Output of this process is a modified reconstructed picture beforein-loop filtering.

The derivation process for quantization parameters as specified inclause 8.7.1 is invoked with the luma location (xCb, yCb ), the width ofthe current coding block in luma samples cbWidth and the height of thecurrent coding block in luma samples cbHeight, and the variable treeTypeas inputs.

When treeType is equal to SINGLE_TREE or treeType is equal toDUAL_TREE_LUMA, the decoding process for luma samples is specified asfollows:

-   If pcm_flag[ xCb ][ yCb ] is equal to 1, the reconstructed picture    is modified as follows:

$\begin{array}{l}{S_{L}\lbrack xCb + i\rbrack\lbrack yCb + j\rbrack =} \\{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, pcm\_ sample\_ luma\lbrack(cbHeight*j) + i\rbrack < <} \\{\,\,\,\,\,\,\,\,\,\,(BitDepth_{Y} - PcmBitDepth_{Y}),} \\{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, with\mspace{6mu} i = 0..cbWidth - 1,j = 0..cbHeight - 1}\end{array}$

-   Otherwise, the following applies:    -   1. The luma intra prediction mode is derived as follows:        -   If intra lwip_flag[ xCb ][ yCb ] is equal to 1, the            derivation process for the affine linear weighted intra            prediction mode as specified in clause 8.4.X is invoked with            the luma location ( xCb, yCb ), the width of the current            coding block in luma samples cbWidth and the height of the            current coding block in luma samples cbHeight as input.        -   Otherwise, the derivation process for the luma intra            prediction mode as specified in clause 8.4.2 is invoked with            the luma location ( xCb, yCb ), the width of the current            coding block in luma samples cbWidth and the height of the            current coding block in luma samples cbHeight as input.    -   2. The general decoding process for intra blocks as specified in        clause 8.4.4.1 is invoked with the luma location ( xCb, yCb),        the tree type treeType, the variable nTbW set equal to cbWidth,        the variable nTbH set equal to cbHeight, the variable        predModelntra set equal to IntraPredModeY[ xCb ][ yCb ], and the        variable cldx set equal to 0 as inputs, and the output is a        modified reconstructed picture before in-loop filtering.

<Begin> 8.4.x Derivation Process for Affine Linear Weighted IntraPrediction Mode

Input to this process are:

-   a luma location ( xCb, yCb ) specifying the top-left sample of the    current luma coding block relative to the top-left luma sample of    the current picture,-   a variable cbWidth specifying the width of the current coding block    in luma samples,-   a variable cbHeight specifying the height of the current coding    block in luma samples.

In this process, the affine linear weighted intra prediction modeIntraPredModeY[ xCb ][ yCb ] is derived. IntraPredModeY[ xCb ][ yCb ] isderived by the following ordered steps:

-   1. The neighboring locations ( xNbA, yNbA) and ( xNbB, yNbB) are set    equal to ( xCb-1, yCb ) and ( xCb, yCb - 1 ), respectively.-   2. For X being replaced by either A or B, the variables    candLwipModeX are derived as follows:    -   The availability derivation process for a block as specified in        clause 6.4.X [Ed. (BB): Neighboring blocks availability checking        process tbd] is invoked with the location ( xCurr, yCurr ) set        equal to ( xCb, yCb ) and the neighboring location ( xNbY, yNbY)        set equal to ( xNbX, yNbX) as inputs, and the output is assigned        to availableX.    -   The candidate affine linear weighted intra prediction mode        candLwipModeX is derived as follows:        -   If one or more of the following conditions are true,            candLwipModeX is set equal to -1.            -   The variable availableX is equal to FALSE.            -   CuPredMode[ xNbX ][ yNbX ] is not equal to MODE_INTRA                and mh_intra_flag[ xNbX ][ yNbX ] is not equal to 1.            -   pcm_flag[ xNbX ][ yNbX ] is equal to 1.            -   X is equal to B and yCb -1 is less than ((yCb >>                CtbLog2SizeY) << CtbLog2SizeY).        -   Otherwise, the following applies:            -   The size type derivation process for a block as                specified in clause 8.4.X.1 is invoked with the width of                the current coding block in luma samples cbWidth and the                height of the current coding block in luma samples                cbHeight as input, and the output is assigned to                variable sizeld.        -   If intra lwip_flag[ xNbX ][ yNbX ] is equal to 1, the size            type derivation process for a block as specified in clause            8.4.X.1 is invoked with the width of the neighboring coding            block in luma samples nbWidthX and the height of the            neighboring coding block in luma samples nbHeightX as input,            and the output is assigned to variable sizeldX.            -   If sizeld is equal to sizeldX, candLwipModeX is set                equal to IntraPredModeY[ xNbX ][ yNbX ].            -   Otherwise, candLwipModeX is set equal to -1.        -   Otherwise, candLwipModeX is derived using IntraPredModeY[            xNbX ][ yNbX ] and sizeld as specified in Table 8-X1.-   3. The candLwipModeList[ x ] with x = 0..2 is derived as follows,    using lwipMpmCand[ sizeld ] as specified in Table 8-X2:    -   If candLwipModeA and candLwipModeB are both equal to -1, the        following applies:    -   candLwipModeList[0] = IwipMpmCand[sizeId][0]    -   candLwipModeList[1] = IwipMpmCand[sizeId][1]    -   candLwipModeList[2] = IwipMpmCand[sizeId][2]    -   Otherwise, the following apllies:        -   If candLwipModeA is equal to candLwipModeB or if either            candLwipModeA or candLwipModeB is equal to -1, the following            applies:        -   $\begin{array}{l}            {candLwipModeList\lbrack 0\rbrack = \left( {candLwipModeA!\mspace{2mu} = - 1} \right)?} \\            {candLwipModeA:candLwipModeB}            \end{array}$        -   If candLwipModeList is equal to lwipMpmCand[sizeld], the            following applies:        -   candLwipModeList[1] = lwipMpmCand[sizeId][1]        -   candLwipModeList[2] = lwipMpmCand[sizeId][2]        -   Otherwise, the following applies:        -   candLwipModeList[1] = lwipMpmCand[sizeId][0]        -   $\begin{array}{l}            {candLwipModeList\lbrack 2\rbrack = \left( {candLwipModeList\lbrack 0\rbrack! =} \right)} \\            {\left( {lwipMpmCand\left\lbrack {sizeId} \right\rbrack\lbrack 1\rbrack} \right)\mspace{6mu}?\mspace{6mu} lwipMpmCand\left\lbrack {sizeId} \right\rbrack\lbrack 1\rbrack:} \\            {lwipMpmCand\left\lbrack {sizeId} \right\rbrack\lbrack 2\rbrack}            \end{array}$        -   Otherwise, the following applies:        -   candLwipModeList[0] = candLwipModeA        -   candLwipModeList[1] = candLwipModeB        -   If candLwipModeA and candLwipModeB are both not equal to            lwipMpmCand[sizeld], the following applies:        -   candLwipModeList[2] = IwipMpmCand[sizeId][0]    -   Otherwise, the following applies:        -   If candLwipModeA and candLwipModeB are both not equal to            lwipMpmCand[sizeld], the following applies:        -   candLwipModeList[2] = IwipMpmCand[sizeId][1]        -   Otherwise, the following applies:    -   candLwipModeList[2] = IwipMpmCand[sizeId][2]-   4. IntraPredModeY[ xCb ][ yCb ] is derived by applying the following    procedure:    -   If intra_lwip_mpm_flag[ xCb ][ yCb ] is equal to 1, the        IntraPredModeY[ xCb ][yCb ] is set equal to candLwipModeList[        intra_lwip_mpm_idx[ xCb ][ yCb ] ].    -   Otherwise, IntraPredModeY[ xCb ][ yCb ] is derived by applying        the following ordered steps:        -   1. When candLwipModeList[ i ] is greater than            candLwipModeList[ j ] for i = 0..1 and for each i, j = ( i +            1 )..2, both values are swapped as follows:        -   $\begin{array}{l}            {\left( {candLwipModeList\lbrack i\rbrack,\, candLwipModeList\lbrack j\rbrack} \right) =} \\            {Swap\left( {candLwipModeList\lbrack i\rbrack,\, candLwipMode\lbrack j\rbrack} \right)}            \end{array}$        -   2. IntraPredModeY[ xCb ][ yCb ] is derived by the following            ordered steps:            -   i. IntraPredModeY[ xCb ][ yCb ] is set equal to intra                lwip_mpm_remainder[ xCb ][ yCb ].            -   ii. For i equal to 0 to 2, inclusive, when                IntraPredModeY[ xCb ][ yCb ] is greater than or equal to                candLwipModeList[ i ], the value of IntraPredModeY[ xCb                ][ yCb ] is incremented by one.

The variable IntraPredModeY[ x ][ y ] with x = xCb..xCb + cbWidth -1 andy = yCb..yCb + cbHeight -1 is set to be equal to IntraPredModeY[ xCb ][yCb ].

8.4.X.1 Derivation Process for Prediction Block Size Type

Input to this process are:

-   a variable cbWidth specifying the width of the current coding block    in luma samples,-   a variable cbHeight specifying the height of the current coding    block in luma samples.

Output of this process is a variable sizeld.

The variable sizeld is derived as follows:

-   If both cbWidth and cbHeight are equal to 4, sizeld is set equal to    0.-   Otherwise, if both cbWidth and cbHeight are less than or equal to 8,    sizeld is set equal to 1.-   Otherwise, sizeld is set equal to 2.

Table 8-X1 Specification of mapping between intra prediction and affinelinear weighted intra prediction modes IntraPredModeY[ xNbX ][ yNbX ]block size type sizeId 0 1 2 0 17 0 5 1 17 0 1 2, 3 17 10 3 4, 5 9 10 36, 7 9 10 3 8, 9 9 10 3 10, 11 9 10 0 12, 13 17 4 0 14, 15 17 6 0 16, 1717 7 4 18, 19 17 7 4 20, 21 17 7 4 22, 23 17 5 5 24, 25 17 5 1 26, 27 50 1 28, 29 5 0 1 30, 31 5 3 1 32, 33 5 3 1 34, 35 34 12 6 36, 37 22 12 638, 39 22 12 6 40, 41 22 12 6 42, 43 22 14 6 44, 45 34 14 10 46, 47 3414 10 48, 49 34 16 9 50, 51 34 16 9 52, 53 34 16 9 54, 55 34 15 9 56, 5734 13 9 58, 59 26 1 8 60, 61 26 1 8 62, 63 26 1 8 64, 65 26 1 8 66 26 18

Table 8-X2 Specification of affine linear weighted intra predictioncandidate modes candidate mode 0 1 2 iwipMpmCand[ 0 ] 17 34 5iwipMpmCand[ 1 ] 0 7 16 iwipMpmCand[ 2 ] 1 4 6

<end> 8.4.2. Derivation Process for Luma Intra Prediction Mode

Input to this process are:

-   a luma location ( xCb, yCb ) specifying the top-left sample of the    current luma coding block relative to the top-left luma sample of    the current picture,-   a variable cbWidth specifying the width of the current coding block    in luma samples,-   a variable cbHeight specifying the height of the current coding    block in luma samples.

In this process, the luma intra prediction mode IntraPredModeY[ xCb ][yCb ] is derived. Table 8-1 specifies the value for the intra predictionmode IntraPredModeY[ xCb ][ yCb ] and the associated names.

Table 8-1 Specification of intra prediction mode and associated namesIntra prediction mode Associated name 0 INTRA_PLANAR 1 INTRA_DC 2..66INTRA_ANGULAR2..INTRA_ANGULAR66 81..83 INTRA_LT_CCLM, INTRA_L_CCLM,INTRA_T_CCLM NOTE-: The intra prediction modes INTRA_LT_CCLM,INTRA_L_CCLM and INTRA_T_CCLM are only applicable to chroma components.

IntraPredModeY[ xCb ][ yCb ] is derived by the following ordered steps:

-   1. The neighboring locations ( xNbA, yNbA ) and ( xNbB, yNbB) are    set equal to ( xCb -1, yCb + cbheight - 1 ) and ( xCb + cbWidth -1,    yCb - 1 ), respectively.-   2. For X being replaced by either A or 8, the variables    candlniraPredModeX are derived as follows:    -   The availability derivation process for a block as specified in        clause <begin>6.4.X [Ed. (BB): Neighboring blocks availability        checking process tbd] <end>is invoked with the location (xCurr,        yCurr) set equal to ( xCb, yCb ) and the neighboring location (        xNbY, yNbY ) set equal to ( xNbX, yNbX ) as inputs, and the        output is assigned to availableX.    -   The candidate intra prediction mode candlntraPredModeX is        derived as follows:        -   If one or more of the following conditions are true,            candlntraPredModeX is set equal to INTRA_PLANAR.            -   The variable availableX is equal to FALSE.            -   CuPredMode[ xNbX ][ yNbX ] is not equal to MODE_INTRA                and ciip_flog[ xNbX ][ yNbX ] is not equal to 1.            -   pcm_flag[ xNbX ][ yNbX ] is equal to 1.            -   X is equal to B and yCb -1 is less than ( ( yCb »                CtbLog2SizeY) « CtbLog2SizeY).        -   Otherwise, candlntraPredModeX is derived as follows:            -   If intra lwip_flag[ xCb ][ yCb ] is equal to 1,                candlntraPredModeX is derived by the following ordered                steps:                -   i. The size type derivation process for a block as                    specified in clause 8.4.X.1 is invoked with the                    width of the current coding block in luma samples                    cbWidth and the height of the current coding block                    in luma samples cbHeight as input, and the output is                    assigned to variable sizeld.                -   ii. candlntraPredModeX is derived using                    IntraPredModeY[ xNbx ][ yNbX ] and sizeld as                    specified in Table 8-X3.            -   Otherwise, candlntraPredModeX is set equal to                IntraPredModeY[ xNbX ][ yNbX ].-   3. The variables ispDefaultModel1 and ispDefaultMode2 are defined as    follows:    -   If IntraSubPartitionsSplitType is equal to ISP_HOR_SPLlT,        ispDefaultModel1 is set equal to INTRA_ANGULAR18 and        ispDefaultMode2 is set equal to INTRA_ANGULAR5.    -   Otherwise, ispDefaultModel1 is set equal to INTRA_ANGULAR50 and        ispDefaultMode2 is set equal to INTRA_ANGULAR63.

Table 8-X3 Specification of mapping between affine linear weighted intraprediction and intra prediction modes IntraPredModeY[ xNbX ][ yNbX ]block size type sizeId 0 1 2 0 0 0 1 1 18 1 1 2 18 0 1 3 0 1 1 4 18 0 185 0 22 0 6 12 18 1 7 0 18 0 8 18 1 1 9 2 0 50 10 18 1 0 11 12 0 12 18 113 18 0 14 1 44 15 18 0 16 18 50 17 0 1 18 0 0 19 50 20 0 21 50 22 0 2356 24 0 25 50 26 66 27 50 28 56 29 50 30 50 31 1 32 50 33 50 34 50

8.4.3 Derivation Process for Chroma Intra Prediction Mode

Input to this process are:

-   a luma location ( xCb, yCb ) specifying the top-left sample of the    current chroma coding block relative to the top-left luma sample of    the current picture,-   a variable cbWidth specifying the width of the current coding block    in luma samples,-   a variable cbHeight specifying the height of the current coding    block in luma samples.

In this process, the chroma intra prediction mode IntraPredModeC[ xCb ][yCb ] is derived.

The corresponding luma intra prediction mode lumalntraPredMode isderived as follows:

-   If intra_lwip_flag[ xCb ][ yCb ] is equal to 1, lumalntraPredMode is    derived by the following ordered steps:    -   i. The size type derivation process for a block as specified in        clause 8.4.X.1 is invoked with the width of the current coding        block in luma samples cbWidth and the height of the current        coding block in luma samples cbHeight as input, and the output        is assigned to variable sizeld.    -   ii. The luma intra prediction mode is derived using        IntraPredModeY[ xCb + cbWidth /2 ][ yCb + cbHeight/2] and sizeld        as specified in Table 8-X3 and assigning the value of        candlntraPredModeX to lumalntraPredMode.-   Otherwise, lumalntraPredMode is set equal to IntraPredModeY[ xCb +    cbWidth / 2 ][ yCb + cbHeight ].

The chroma intra prediction mode IntraPredModeC[ xCb ][ yCb ] is derivedusing intra_chroma pred_mode[ xCb ][ yCb ] and lumalntraPredMode asspecified in Table 8-2 and Table 8-3.

XXX. Intra Sample Prediction <Begin>

Inputs to this process are:

-   α sample location ( xTbCmp, yTbCmp ) specifying the top-left sample    of the current transform block relative to the top-left sample of    the current picture,-   α variable predmodelntra specifying the intra prediction mode,-   α variable nTbW specifying the transform block width,-   α variable nTbH specifying the transform block height,-   α variable nCbW specifying the coding block width,-   α variable nCbH specifying the coding block height,-   α variable cldx specifying the colour component of the current    block.

Outputs of this process are the predicted samples predSamples[ x ][ y ],with x = O..nTbW - 1, y = O..nTbH -1.

The predicted samples predSamples[ x ][ y ] are derived as follows:

-   If intra lwip_flag[ xTbCmp ][ yTbCmp ] is equal to 1 and cldx is    equal to 0, the affine linear weighted intra sample prediction    process as specified in clause 8.4.4.2.X1 is invoked with the    location ( xTbCmp, yTbCmp ), the intra prediction mode    predModelntra, the transform block width nTbW and height nTbH as    inputs, and the output is predSamples.-   Otherwise, the general intra sample prediction process as specified    in clause 8.4.4.2.X1. is invoked with the location ( xTbCmp,    yTbCmp), the intra prediction mode predModeIntra, the transform    block width nTbW and height nTbH, the coding block width nCbW and    height nCbH, and the variable cldx as inputs, and the output is    predSamples.

8.4.4.2.X1 Affine Linear Weighted Intra Sample Prediction

Inputs to this process are:

-   a sample location ( xTbCmp, yTbCmp ) specifying the top-left sample    of the current transform block relative to the top-left sample of    the current picture,-   a variable predModeIntra specifying the intra prediction mode,-   a variable nTbW specifying the transform block width,-   a variable nTbH specifying the transform block height.

Outputs of this process are the predicted samples predSamples[ x ][ y ],with x = 0..nTbW - 1, y = 0..nTbH - 1.

The size type derivation process for a block as specified in clause8.4.X.1 is invoked with the transform block width nTbW and the transformblock height nTbH as input, and the output is assigned to variablesizeld.

Variables numModes, boundarySize, predW, predH and predC are derivedusing sizeld as specified in Table 8-X4.

Table 8-X4 Specification of number of modes, boundary sample size andprediction sizes depending on sizeld sizeId numModes boundarySize predWpredH predC 0 35 2 4 4 4 1 19 4 4 4 4 2 11 4 Min( nTbW, 8 ) Min( nTbH, 8) 8

The flag is Transposed is derived as follows:

isTransposed = (predModelntra > (numModes/2))?1 : 0

The flags needUpsBdryHor and needUpsBdryVer are derived as follows:

needUpsBdryHor = (nTbW > predW) ? TRUE : FALSE(8 − X16)

needUpsBdryVer = (nTbH > predH) ? TRUE : FALSE(8 − X17)

The variables upsBdryW and upsBdryH are derived as follows:

upsBdryW = (nTbH > nTbW) ? nTbW : predW

upsBdryH = (nTbH > nTbW) ? predH : nTbH

The variables IwipW and IwipH are derived as follows:

IwipW = (isTransposed =  = 1)?predH : predW

IwipH = (isTransposed =  = 1)?predW : predH

For the generation of the reference samples refT[ x ] with x = 0..nTbW -1 and refL[y] with y = 0..nTbH - 1, the reference sample derivationprocess as specified in clause 8.4.4.2.X2 is invoked with the samplelocation ( xTbCmp, yTbCmp ), the transform block width nTbW, thetransform block height nTbH as inputs, and top and left referencesamples refT[ x ] with x = 0..nTbW - 1 and refL[y] with y = 0..nTbH - 1,respectively, as outputs.

For the generation of the boundary samples p[ x ] with x = 0..2 *boundarySize - 1, the following applies:

-   The boundary reduction process as specified in clause 8.4.4.2.X3 is    invoked for the top reference samples with the block size nTbW, the    reference samples refT, the boundary size boundarySize, the    upsampling boundary flag needUpsBdryVer, and the upsampling boundary    size upsBdryW as inputs, and reduced boundary samples redT[ x ] with    x = 0..boundarySize - 1 and upsampling boundary samples upsBdryT[ x    ] with x = 0..upsBdryW - 1 as outputs.-   The boundary reduction process as specified in clause 8.4.4.2.X3 is    invoked for the left reference samples with the block size nTbH, the    reference samples refL, the boundary size boundarySize, the    upsampling boundary flag needUpsBdryHor, and the upsampling boundary    size upsBdryH as inputs, and reduced boundary samples redL[ x ] with    x = 0..boundarySize - 1 and upsampling boundary samples upsBdryL[ x    ] with x = 0..upsBdryH - 1 as outputs.-   The reduced top and left boundary samples redT and redL are assigned    to the boundary sample array p as follows:    -   If isTransposed is equal to 1, p[ x ] is set equal to redL[ x ]        with x = 0..boundarySize - 1 and p[ x + boundarySize] is set        equal to redT[ x ] with x = 0..boundarySize - 1.    -   Otherwise, p[ x ] is set equal to redT[ x ] with x =        0..boundarySize - 1 and p[ x + boundarySize] is set equal to        redL[ x ] with x = 0..boundarySize - 1.

For the intra sample prediction process according to predModeIntra, thefollowing ordered steps apply:

-   1. The affine linear weighted samples predLwip[ x ][y], with x =    0..IwipW - 1, y = 0..IwipH - 1 are derived as follows:    -   The variable modeld is derived as follows:    -   $\begin{array}{l}        {modeId = predModeIntra -} \\        {(isTransposed = = 1)?(numModes/2):0}        \end{array}$    -   The weight matrix mWeight[ x ][ y] with x = 0..2 *        boundarySize - 1, y = 0..predC * predC-1is derived using sizeld        and modeld as specified in Table 8-XX [TBD: add weight        matrices].    -   The bias vector vBias[ y] with y = 0..predC * predC - 1 is        derived using sizeld and modeld as specified in Table 8-XX [TBD:        add bias vectors].    -   The variable sW is derived using sizeld and modeld as specified        in Table 8-X5.    -   The affine linear weighted samples predLwip[ x ][ y], with x =        0..IwipW - 1, y = 0..IwipH - 1 are derived as follows:    -   oW = 1 <  < (sW − 1)    -   sB = BitDepth_(Y) − 1    -   incW = (predC > lwipW)?2 : 1    -   incH = (predC > lwipH)?2 : 1    -   $\begin{array}{l}        {predLwip\lbrack x\rbrack\lbrack y\rbrack =} \\        {\left( \left( {\sum_{i = 0}^{2\mspace{6mu} \ast \mspace{6mu} boundarySize - 1}{mWeight\lbrack i\rbrack\left\lbrack {y \ast incH \ast predC + x \ast incW} \right\rbrack}} \right) \right)} \\        {\left( {\ast p\lbrack i\rbrack} \right) +}        \end{array}$    -   ((vBias[y * incH * predC + x * incW] <  < sB) + oW) >  > sW-   2. The predicted samples predSamples[ x ][ y], with x = 0..nTbW - 1,    y = 0..nTbH - 1 are derived as follows:    -   When is Transposed is equal to 1, predLwip[ x ][ y], with x =        0.. predW - 1, y = 0..predH - 1 is set equal to predLwip[ y][ x        ].    -   If needUpsBdryVer is equal to TRUE or needUpsBdryHor is equal to        TRUE, the prediction upsampling process as specified in clause        8.4.4.2.X4 is invoked with the input block width predW, the        input block height predH, affine linear weighted samples        predLwip, the transform block width nTbW, the transform block        height nTbH, the upsampling boundary width upsBdryW, the        upsampling boundary height upsBdryH, the top upsampling boundary        samples upsBdryT, and the left upsampling boundary samples        upsBdryL as inputs, and the output is the predicted sample array        predSamples.    -   Otherwise, predSamples[ x ][ y], with x = 0..nTbW - 1, y =        0..nTbH - 1 is set equal to predLwip[ x ][ y ].

Table 8-X5 Specification of weight shifts sW depending on sizeld andmodeld modeId sizeId 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 0 8 8 88 8 8 8 8 8 8 8 8 8 8 8 8 8 8 1 8 8 8 9 8 8 8 8 9 8 2 8 8 8 8 8 8

8.4.4.2.X2Reference Sample Derivation Process

Inputs to this process are:

-   a sample location ( xTbY, yTbY ) specifying the top-left luma sample    of the current transform block relative to the top-left luma sample    of the current picture,-   a variable nTbW specifying the transform block width,-   a variable nTbH specifying the transform block height.

Outputs of this process are the top and left reference samples refT[ x ]with x = 0..nTbW - 1 and refL[ y ] with y = 0..nTbH - 1, respectively.

The neighboring samples refT[ x ] with x = 0..nTbW - 1 and refL[ y ]with y = 0..nTbH - 1 are constructed samples prior to the in-loop filterprocess and derived as follows:

-   The top and left neighboring luma locations ( xNbT, yNbT ) and (    xNbL, yNbL ) are specified by:-   ( xNbT, yNbT ) = ( xTbY + x, yTbY − 1 )-   ( xNbL, yNbL ) = ( xTbY − 1, yTbY + y )-   The availability derivation process for a block as specified in    clause 6.4.X [Ed. (BB): Neighboring blocks availability checking    process tbd] is invoked with the current luma location ( xCurr,    yCurr ) set equal to ( xTbY, yTbY ) and the top neighboring luma    location ( xNbT, yNbT ) as inputs, and the output is assigned to    availTop[ x ]with x = 0..nTbW - 1.-   The availability derivation process for a block as specified in    clause 6.4.X [Ed. (BB): Neighboring blocks availability checking    process tbd] is invoked with the current luma location (xCurr,    yCurr) set equal to (xTbY, yTbY) and the left neighboring luma    location (xNbL, yNbL) as inputs, and the output is assigned to    availLeft[ y ] with y = 0..nTbH -1.-   The top reference samples refT[ x ] with × = 0..nTbW -1 are derived    as follows:    -   If all availTop[ x ] with x = 0..nTbW -1 are equal to TRUE, the        sample at the location (xNbT, yNbT) is assigned to refT[ x ]        with x = 0..nTbW -1.    -   Otherwise, if availTop[ 0 ] is equal to FALSE, all reft[ x ]        with x=0..nTbW-1 are set equal to 1 << ( BitDepth_(Y)-1).    -   Otherwise, reference samples refT[ x ] with × = 0..nTbW -1 are        derived by the following ordered steps:        -   1. The variable lastT is set equal to the position × of the            first element in the sequence availTop[ x ] with x = 1..nTbW            -1 that is equal to FALSE.        -   2. For every × = 0..lastT- 1, the sample at the location (            xNbT, yNbT) is assigned to refT[ x ].        -   3. For every × = lastT..nTbW- 1, refT[ x ] is set equal to            refT[ lastT- 1 ].-   The left reference samples refL[ y ] with x = 0..nTbH -1 are derived    as follows:    -   If all availLeft[ y ] with y = 0..nTbH -1 are equal to TRUE, the        sample at the location (xNbL, yNbL) is assigned to refL[ y ]        with y = 0..nTbH -1.    -   Otherwise, if availLeft[ 0 ] is equal to FALSE, all refL[ y ]        with y = 0..nTbH -1 are set equal to 1 << ( BitDepth_(Y)-1).    -   Otherwise, reference samples refL[ y ] with y = 0..n TbH -1 are        derived by the following ordered steps:        -   1. The variable lastL is set equal to the position y of the            first element in the sequence availLeft[ y ] with y =            1..nTbH -1 that is equal to FALSE.        -   2. For every y = 0..lastL -1, the sample at the location            (xNbL, yNbL) is assigned to refL[ y ].        -   3. For every y = lastL..nTbH -1, refL[ y ] is set equal to            refL[ lastL -1].

Specification of the Boundary Reduction Process

Inputs to this process are:

-   a variable nTbX specifying the transform block size,-   reference samples refX[ × ] with × = 0..nTbX - 1,-   a variable boundarySize specifying the downsampled boundary size,-   a flag needUpsBdryX specifying whether intermediate boundary samples    are required for upsampling,-   a variable upsBdrySize specifying the boundary size for upsampling.

Outputs of this process are the reduced boundary samples redX[ x ] with× = 0..boundarySize -1 and upsampling boundary samples upsBdryX[ × ]with × = 0.. upsBdrySize -1.

The upsampling boundary samples upsBdryX[ x ] with x = 0..upsBdrySize -1are derived as follows:

-   If needUpsBdryX is equal to TRUE and upsBdrySize is less than nTbX,    the following applies:-   uDwn = nTbX/upsBdrySize

$\begin{array}{l}{upsBdryX\left\lbrack {\mspace{6mu} x\mspace{6mu}} \right\rbrack\mspace{6mu} = \mspace{6mu}\left( {\sum_{i = 0}^{uDwn - 1}\begin{array}{l}{refX\left\lbrack {\mspace{6mu} x\mspace{6mu} \ast \mspace{6mu} uDwn + i} \right\rbrack +} \\{\left( {\mspace{6mu} 1 \ll \left( {Log2\left( {\mspace{6mu} uDwn} \right)\mspace{6mu}} \right)} \right) - \left( {\left( {1\mspace{6mu}} \right)\mspace{6mu}} \right)}\end{array}} \right)} \\{\gg \mspace{6mu} Log2\left( {\mspace{6mu} uDwn\mspace{6mu}} \right)}\end{array}$

-   Otherwise (upsBdrySize is equal to nTbX), upsBdryX[ x ] is set equal    to refX[ x ].

The reduced boundary samples redx[ x ] with × = 0..boundarySize -1 arederived as follows:

-   If boundarySize is less than upsBdrySize, the following applies:-   bDwn = upsBdrySize/boundarySize

$\begin{array}{l}{redX\left\lbrack {\mspace{6mu} x\mspace{6mu}} \right\rbrack = \left( {\sum_{i = 0}^{bDwn - 1}\begin{array}{l}{upsBdryX\left\lbrack {\mspace{6mu} x\mspace{6mu} \ast \mspace{6mu} bDwn + i} \right\rbrack\mspace{6mu} + \mspace{6mu}} \\\left( {\mspace{6mu} 1\mspace{6mu} \ll \left( {\mspace{6mu} Log2\left( {\mspace{6mu} bDwn\mspace{6mu}} \right)} \right) - (1)\mspace{6mu}} \right)\end{array}} \right)\mspace{6mu}} \\{\gg \mspace{6mu} Log2\left( {\mspace{6mu} bDwn\mspace{6mu}} \right)}\end{array}$

-   Otherwise (boundarySize is equal to upsBdrySize), redX[ x ] is set    equal to upsBdryX[ x ].

8.4.4.2.X4Specification of the Prediction Upsampling Process

Inputs to this process are:

-   a variable predW specifying the input block width,-   a variable predH specifying the input block height,-   affine linear weighted samples predLwip[ x ][ y ], with × = 0..predW    -1, y = 0..predH -1,-   a variable nTbW specifying the transform block width,-   a variable nTbH specifying the transform block height,-   a variable upsBdryW specifying the upsampling boundary width,-   a variable upsBdryH specifying the upsampling boundary height,-   top upsampling boundary samples upsBdryT[ x ] with × = 0..upsBdryW-    1,-   left upsampling boundary samples upsBdryL[ x ] with x =    0..upsBdryH-1.

Outputs of this process are the predicted samples predSamples[ x ][ y ],with × = 0..nTbW -1, y = 0..nTbH -1. The sparse predicted samplespredSamples[ m ][ n ] are derived from predLwip[ x ][ y ], with × =0..predW -1, y = 0..predH -1 as follows:

-   upHor = nTbW/predW-   upVer = nTbH/predH-   $\begin{array}{l}    {predSamples\left\lbrack {\left( {x + 1} \right)*upHor - 1} \right\rbrack\left\lbrack {\left( {y + 1} \right)*upVer - 1} \right\rbrack =} \\    {predLwip\lbrack x\rbrack\lbrack y\rbrack}    \end{array}$

The top boundary samples upsBdryT[ x ] with x = 0..upsBdryW -1 areassigned to predSamples[ m][ -1 ] as follows:

$\begin{array}{l}{predSamples\left\lbrack {\left( {x + 1} \right)*\left( {nTbW/upsBdryW} \right) - 1} \right\rbrack\left\lbrack {- 1} \right\rbrack =} \\{upsBdryT\lbrack x\rbrack}\end{array}$

The left boundary samples upsBdryL[ y ] with y = 0..upsBdryH - 1 areassigned to predSamples[-1 ][n ] as follows:

predSamples[−1][{y + 1) * (nTbH/upsBdryH) − 1] = upsBdryL[y]

The predicted samples predSamples[ x ][ y ], with × = 0..nTbW -1, y =0..nTbH-1 are derived as follows:

-   If nTbH is greater than nTbW, the following ordered steps apply:    -   1. When upHor is greater than 1, hoizontal upsampling for all        sparse positions ( xHor, yHor ) = ( m * upHor-1, n * upVer-1)        with m = 0..predW -1, n = 1..predH is applied with dX = 1..upHor        -1 as follows:        -   $\begin{array}{l}            {predSamples\left\lbrack {xHor + dX} \right\rbrack\left\lbrack {yHor} \right\rbrack =} \\            {((upHor - dX)*predSamples\left\lbrack {xHor} \right\rbrack\left\lbrack {yHor} \right\rbrack +} \\            {dx*predSamples\left\lbrack {xHor + upHor} \right\rbrack\left\lbrack {yHor} \right\rbrack)/upHor}            \end{array}$    -   2. Vertical upsampling for all sparse positions ( xVer, yVer ) =        ( m, n * upVer-1 ) with m = 0..nTbW -1, n = 0..predH - 1 is        applied with dY= 1..upVer -1 as follows:        -   $\begin{array}{l}            {predSamples\left\lbrack {xVer} \right\rbrack\left\lbrack {yVer + dY} \right\rbrack =} \\            {((upVer - dy)*predSamples\left\lbrack {xVer} \right\rbrack\left\lbrack {yVer} \right\rbrack +} \\            {dY*predSamples\left\lbrack {xVer} \right\rbrack\left\lbrack {yVer + upVer} \right\rbrack)/upVer}            \end{array}$-   Otherwise, the following ordered steps apply:    -   1. When upVer is greater than 1, vertical upsampling for all        sparse positions ( xVer, yVer ) = ( m * upHor -1, n * upVer- 1)        with m = 1..predW, n = 0..predH -1 is applied with dY= 1..upVer        -1 as specified in (8-X40).    -   2. Horizontal upsampling for all sparse positions ( xHor, yHor )        = ( m * upHor - 1, n ) with m = 0..predW - 1, n = 0..nTbH - 1 is        applied with dX = 1..upHor - 1 as specified in (8-X39).

<end>

Table 9-9 Syntax elements and associated binarizations Syntax structureSyntax element Binarization Process Input parameters coding­_unit( )cu_skip_flag[ ][ ] FL cMax = 1 pred_mode_ibc_flag FL cMax = 1pred_mode_flag FL cmax = 1 <begin>intra_lwip_flag[ ][ ] FL cmax = 1intra_lwip_mpm_flag[ ] [ ] FL cmax = 1 intra_lwip_mpm_idx[ ][ ] TR cMax= 2, cRiceParam = 0 intra_lwip_mpm_remainder[ ][ ] FL cmax = (cbWidth == 4 && cbHeight= = 4) ? 31 : ((cbWidth <= 8 && cbHeight<= 8) ? 15 : 7)...

Table 9-15 Assignment of ctxInc to syntax elements with context codedbins Syntax element binIdx 0 1 2 3 4 >= 5 ... terminate na na na na naintra_lwip_flag[ ][ ] (Abs( Log2(cbWidth)-Log2(cbHeight))> 1) ? 3 :(0,1,2 (clause 9.5.4.2.2) ) na na na na na intra_lwip_mpmflag[ ][ ] 0 nana na na na intra_lwip_mpm_idx[ ][ ] bypass bypass na na na naintra_lwip_mpm_remainder[ ][ ] bypass bypass bypass bypass bypass na

Table 9-16 Specification of ctxlnc using left and above syntax elementsSyntax element condL condA ctxSetIdx ... intra_lwip_flag[ x0 ][ y0 ]intra_lwip_flag[ xNbL ][ yNbL ] intra_lwip_flag[ xNbA ][ yNbA ] 0 ...

<end> Summary of ALWIP

For predicting the samples of a rectangular block of width W and heightH, affine linear weighted intra prediction (ALWIP) takes one line of Hreconstructed neighboring boundary samples left of the block and oneline of W reconstructed neighboring boundary samples above the block asinput. If the reconstructed samples are unavailable, they are generatedas it is done in the conventional intra prediction. ALWIP is onlyapplied to luma intra block. For chroma intra block, the conventionalintra coding modes are applied.

The generation of the prediction signal is based on the following threesteps:

1. Out of the boundary samples, four samples in the case of W=H=4 andeight samples in all other cases are extracted by averaging.

2. A matrix vector multiplication, followed by addition of an offset, iscarried out with the averaged samples as an input. The result is areduced prediction signal on a subsampled set of samples in the originalblock.

3. The prediction signal at the remaining positions is generated fromthe prediction signal on the subsampled set by linear interpolationwhich is a single step linear interpolation in each direction.

If an ALWIP mode is to be applied, the index predmode of the ALWIP modeis signaled using a MPM-list with 3 MPMs. Here, the derivation of theMPMs is performed using the intra-modes of the above and the left PU asfollows. There are three fixed tables map_angular_to_alwip_(idx), idx ∈{0,1,2} that assign to each conventional intra prediction modepredmode_(Angular) an ALWIP mode

predmode_(ALWIP) = map_angular_to_alwip_(idx)[predmode_(Angular)].

For each PU of width W and height H one defines an index

idx(PU) = idx(W, H) ∈ {0, 1, 2}

that indicates from which of the three sets the ALWIP-parameters are tobe taken.

If the above Prediction Unit PU_(above) is available, belongs to thesame CTU as the current PU and is in intra mode, if idx(PU) =idx(PU_(above)) and if ALWIP is applied on PU_(above) with ALWIP-modepredmode ALWIPabove , one puts:

mode_(ALWIP)^(above) = predmode_(ALWIP)^(above)   .

If the above PU is available, belongs to the same CTU as the current PUand is in intra mode and if a conventional intra prediction modepredmode above Angular is applied on the above PU, one puts:

mode_(ALWIP)^(above) = map_angular_to_alwip_(idx(PU_(above)))[predmode_(Angular)^(above)] .

In all other cases, one puts:

mode_(ALWIP)^(above) = −1

which means that this mode is unavailable. In the same way but withoutthe restriction that the left PU needs to belong to the same CTU as thecurrent PU, one derives a mode

mode_(ALWIP)^(left).

Finally, three fixed default lists list_(idx), idx ∈ {0,1,2} areprovided, each of which contains three distinct ALWIP modes. Out of thedefault list list_(idx(PU)) and the modes

mode_(ALWIP)^(above)

and

mode_(ALWIP)^(left)

, one constructs three distinct MPMs by substituting -1 by defaultvalues as well as eliminating repetitions.

For the luma MPM-list derivation, whenever a neighboring luma block isencountered which uses an ALWIP-mode predmode _(ALWIP,) this block istreated as if it was using the conventional intra-prediction modepredmode_(Angular).

predmode_(Angular) = map_alwip_to_angular_(idx(PU))[predmode_(ALWIP)]

3 Transform in VVC 3.1 Multiple Transform Selection (MTS)

In addition to Discrete Cosine Transform (DCT)-II which has beenemployed in HEVC, a Multiple Transform Selection (MTS) scheme is usedfor residual coding both inter and intra coded blocks. It uses multipleselected transforms from the DCT8/DST7. The newly introduced transformmatrices are Discrete Sine Transform (DST)-VII and DCT-VIII.

3.2 Reduced Secondary Transform (RST) Proposed in JVET-N0193

Reduced secondary transform (RST) applies 16×16 and 16×64 non-separabletransform for 4×4 and 8×8 blocks, respectively. Primary forward andinverse transforms are still performed the same way as two onedimensional (1-D) horizontal/vertical transform passes. Secondaryforward and inverse transforms are a separate process step from that ofprimary transforms. For encoder, primary forward transform is performedfirst, then followed by secondary forward transform and quantization,and context-adaptive binary arithmetic coding (CABAC) bit encoding. Fordecoder, CABAC bit decoding and inverse quantization, then Secondaryinverse transform is performed first, then followed by primary inversetransform. RST applies only to intra coded transform units (TUs) in bothintra slice and inter slices.

3.3 A Unified MPM List for Intra Mode Coding in JVET-N0185

A unified 6-MPM list is proposed for intra blocks irrespective ofwhether Multiple Reference Line (MRL) and Intra sub-partition (ISP)coding tools are applied or not. The MPM list is constructed based onintra modes of the left and above neighboring block as in VVC Test Model4.0 (VTM4.0). Suppose the mode of the left is denoted as Left and themode of the above block is denoted as Above, the unified MPM list isconstructed as follows:

-   When a neighboring block is not available, its intra mode is set to    Planar by default.-   If both modes Left and Above are non-angular modes:    -   a. MPM list → {Planar, DC, V, H, V-4, V+4}-   If one of modes Left and Above is angular mode, and the other is    non-angular:    -   b. Set a mode Max as the larger mode in Left and Above    -   c. MPM list → {Planar, Max, DC, Max -1, Max +1, Max -2}-   If Left and Above are both angular and they are different:    -   d. Set a mode Max as the larger mode in Left and Above    -   e. if the difference of mode Left and Above is in the range of 2        to 62, inclusive        -   i. MPM list → {Planar, Left, Above, DC, Max -1, Max +1 }    -   f. Otherwise        -   i. MPM list → {Planar, Left, Above, DC, Max -2, Max +2}

Besides, the first bin of the MPM index codeword is CABAC context coded.In total three contexts are used, corresponding to whether the currentintra block is MRL enabled, ISP enabled, or a normal intra block.

The left neighboring block and above neighboring block used in theunified MPM list construction is A2 and B2 as shown in FIG. 10 .

One MPM flag is firstly coded. If the block is coded with one of mode inthe MPM list, an MPM index is further coded. Otherwise, an index to theremaining modes (excluding MPMs) is coded.

4 Examples of Drawbacks in Existing Implementations

The design of ALWIP in JVET-N0217 has the following problems:

-   1) At the March 2019 JVET meeting, a unified 6-MPM list generation    was adopted for MRL mode, ISP mode, and normal intra mode. But the    affine linear weighted prediction mode uses a different 3-MPM list    construction which makes the MPM list construction complicated. A    complex MPM list construction might compromise the throughput of the    decoder, in particular for small blocks such as 4×4 samples.-   2) ALWIP is only applied to luma component of the block. For the    chroma component of an ALWP coded block, a chroma mode index is    coded and sent to decoder, which could result in unnecessary    signaling.-   3) The interactions of ALWIP with other coding tools should be    considered.-   4) When calculating upsBdryX in upsBdryX-   $\left\lbrack {\mspace{6mu}\text{x}\mspace{6mu}} \right\rbrack = \left( {\mspace{6mu}{\sum_{\text{i}\mspace{6mu}\text{=}\mspace{6mu}\text{0}}^{\text{uDwn} - \text{1}}{\text{refX}\left\lbrack {\mspace{6mu}\text{x}\mspace{6mu} \ast \mspace{6mu}\text{uDwn} + \text{i}} \right\rbrack +}}} \right)$-   ( 1  ≪ ( Log2( uDwn ) − (1) )) ≫ Log2( uDwn )   (8 − X31),-   it is possible that Log2( uDwn ) - 1 is equal to -1, while left    shifted with -1 is undefined.-   5) When upsampling the prediction samples, no rounding is applied.-   6) In the deblocking process, ALWIP coded blocks are treated as    normal intra-blocks.

5 Exemplary Methods for Matrix-based Intra Coding

Embodiments of the presently disclosed technology overcome drawbacks ofexisting implementations, thereby providing video coding with highercoding efficiencies but lower computational complexity. Matrix-basedintra prediction methods for video coding, and as described in thepresent document, may enhance both existing and future video codingstandards, is elucidated in the following examples described for variousimplementations. The examples of the disclosed technology provided belowexplain general concepts, and are not meant to be interpreted aslimiting. In an example, unless explicitly indicated to the contrary,the various features described in these examples may be combined.

In the following discussion, an intra-prediction mode refers to anangular intra prediction mode (including DC, planar, CCLM and otherpossible intra prediction modes); while an intra mode refers to normalintra mode, or MRL, or ISP or ALWIP.

In the following discussion, “Other intra modes” may refer to one ormultiple intra modes except ALWIP, such as normal intra mode, or MRL, orISP.

In the following discussion, SatShift(x, n) is defined as

$SatShift\left( {x,\, n} \right) = \left\{ \begin{matrix}{\left( {x + offsset0} \right)\mspace{6mu} \gg n} & {if} & {x \geq 0} \\{- \left( \left( {- x + offset1} \right) \right)\mspace{6mu} \gg (n)} & {if} & {x < 0}\end{matrix} \right)$

Shift(x, n) is defined as Shift(x, n) = (x+ offset0)>>n.

In one example, offset0 and/or offset1 are set to (1<<n)>>1 or(1«(n-1)). In another example, offset0 and/or offset1 are set to 0.

In another example, offset0=offset1= ((1<<n)>>1)-1or ((1«(n-1)))-1.

Clip3(min, max, x) is defined as

$Clip3\left( {Min,\, Max,\, x} \right) = \left\{ \begin{matrix}{Min} & {if} & {x < Min} \\{Max} & {if} & {x > Max} \\x & & {Otherwise}\end{matrix} \right)$

MPM List Construction for ALWIP

1. It is proposed that the whole or partial of the MPM list for ALWIPmay be constructed according to the whole or partial procedure toconstruct the MPM list for non-ALWIP intra mode (such as normal intramode, MRL, or ISP).

-   a. In one example, the size of the MPM list for ALWIP may be the    same as that of the MPM list for non-ALWIP intra mode.    -   i. For example, the size of MPM list is 6 for both ALWIP and        non-ALWIP intra modes.-   b. In one example, the MPM list for ALWIP may be derived from the    MPM list for non-ALWIP intra mode.    -   i. In one example, the MPM list for non-ALWIP intra mode may be        firstly constructed. Afterwards, partial or all of them may be        converted to the MPMs which may be further added to the MPM list        for ALWIP coded blocks.        -   1) Alternatively, furthermore, when adding a converted MPM            to the MPM list for ALWIP coded blocks, pruning may be            applied.        -   2) Default modes may be added to the MPM list for ALWIP            coded blocks.            -   a. In one example, default modes may be added before                those converted from the MPM list of non-ALWIP intra                mode.            -   b. Alternatively, default modes may be added after those                converted from the MPM list of non-ALWIP intra mode.            -   c. Alternatively, default modes may be added in an                interleaved way with those converted from the MPM list                of non-ALWIP intra mode.            -   d. In one example, the default modes may be fixed to be                the same for all kinds of blocks.            -   e. Alternatively, the default modes may be determined                according to coded information, such as availability of                neighboring blocks, mode information of neighboring                blocks, block dimension.    -   ii. In one example, one intra-prediction mode in the MPM list        for non-ALWIP intra mode may be converted to its corresponding        ALWIP intra-prediction mode, when it is put into the MPM list        for ALWIP.        -   1) Alternatively, all the intra-prediction modes in the MPM            list for non-ALWIP intra modes may be converted to            corresponding ALWIP intra-prediction modes before being used            to construct the MPM list for ALWIP.        -   2) Alternatively, all the candidate intra-prediction modes            (may include the intra-prediction modes from neighboring            blocks and default intra-prediction modes such as Planar            and DC) may be converted to corresponding ALWIP            intra-prediction modes before being used to construct the            MPM list for non-ALWIP intra modes, if the MPM list for            non-ALWIP intra modes may be further used to derive the MPM            list for ALWIP.        -   3) In one example, two converted ALWIP intra-prediction            modes may be compared.            -   a. In one example, if they are the same, only one of                them may be put into the MPM list for ALWIP.            -   b. In one example, if they are the same, only one of                them may be put into the MPM list for non-ALWIP intra                modes.    -   iii. In one example, K out of S intra-prediction modes in the        MPM list for non-ALWIP intra modes may be picked as the MPM list        for ALWIP mode. E.g., K is equal to 3 and S is equal to 6.        -   1) In one example, the first K intra-prediction modes in the            MPM list for non-ALWIP intra modes may be picked as the MPM            list for ALWIP mode.

2.It is proposed that the one or multiple neighboring blocks used toderive the MPM list for ALWIP may also be used to used derive the MPMlist for non-ALWIP intra modes (such as normal intra mode, MRL, or ISP).

-   a. In one example, the neighboring block left to the current block    used to derive the MPM list for ALWIP should be the same as that    used to derive the MPM list for non-ALWIP intra modes.    -   i. Suppose the top-left corner of the current block is (xCb,        yCb), the width and height of the current block are W and H,        then in one example, the left neighboring block used to derive        the MPM list for both ALWIP and non-ALWIP intra modes may cover        the position (xCb-1, yCb). In an alternative example, the left        neighboring block used to derive the MPM list for both ALWIP and        non-ALWIP intra modes may cover the position (xCb-1, yCb+H-1).    -   ii. For example, the left neighboring block and above        neighboring block used in the unified MPM list construction is        A2 and B2 as shown in FIG. 10 .-   b. In one example, the neighboring block above to the current block    used to derive the MPM list for ALWIP should be the same as that    used to derive the MPM list for non-ALWIP intra modes.    -   i. Suppose the top-left corner of the current block is (xCb,        yCb), the width and height of the current block are W and H,        then in one example, the above neighboring block used to derive        the MPM list for both ALWIP and non-ALWIP intra modes may cover        the position (xCb, yCb-1). In an alternative example, the above        neighboring block used to derive the MPM list for both ALWIP and        non-ALWIP intra modes may cover the position (xCb+W-1, yCb-1).    -   ii. For example, the left neighboring block and above        neighboring block used in the unified MPM list construction is        A1 and B1 as shown in FIG. 10 .

3.It is proposed that the MPM list for ALWIP may be constructed indifferent ways according to the width and/or height of the currentblock.

-   a. In one example, different neighboring blocks may be accessed for    different block dimensions.

4.It is proposed that the MPM list for ALWIP and the MPM list fornon-ALWIP intra modes may be constructed with the same procedure butwith different parameters.

-   a. In one example, K out of S intra-prediction modes in the MPM list    construction procedure of non-ALWIP intra modes may be derived for    the MPM list used in ALWIP mode. E.g., K is equal to 3 and S is    equal to 6.    -   i. In one example, the first K intra-prediction modes in the MPM        list construction procedure may be derived for the MPM list used        in ALWIP mode.-   b. In one example, the first mode in the MPM list may be different.    -   i. For example, the first mode in the MPM list for non-ALWIP        intra modes may be Planar, but it may be a Mode X0 in the MPM        list for ALWIP.        -   1) In one example, XO may be the ALWIP intra-prediction mode            converted from Planar.-   c. In one example, stuffing modes in the MPM list may be different.    -   i. For example, the first three stuffing modes in the MPM list        for non-ALWIP intra modes may be DC, Vertical and Horizontal,        but they may be Mode X1, X2, X3 in the MPM list for ALWIP.        -   1) In one example, X1, X2, X3 may be different for different            sizeId.    -   ii. In one example, the number of stuffing mode may be        different.-   d. In one example, neighboring modes in the MPM list may be    different.    -   i. For example, the normal intra-prediction modes of neighboring        blocks are used to construct the MPM list for non-ALWIP intra        modes. And they are converted to ALWIP intra-prediction modes to        construct the MPM list for ALWIP mode.-   e. In one example, the shifted modes in the MPM list may be    different.    -   i. For example, X+K0 where X is a normal intra-prediction mode        and K0 is an integer may be put into the MPM list for non-ALWIP        intra modes. And Y+K1 where Y is an ALWIP intra-prediction mode        and K1 is an integer may be put into the MPM list for ALWIP,        where K0 may be different from K1.        -   1) In one example, K1 may depend on the width and height.

5. It is proposed that a neighboring block is treated as unavailable ifit is coded with ALWIP when constructing the MPM list for the currentblock with non-ALWIP intra modes.

-   a. Alternatively, a neighboring block is treated as being coded with    a predefined intra-prediction mode (such as Planar) if it is coded    with ALWIP when constructing the MPM list for the current block with    non-ALWIP intra modes.

6. It is proposed that a neighboring block is treated as unavailable ifit is coded with non-ALWIP intra modes when constructing the MPM listfor the current block with ALWIP mode.

-   a. Alternatively, a neighboring block is treated as being coded with    a predefined ALWIP intra-prediction mode X if it is coded with    non-ALWIP intra modes when constructing the MPM list for the current    block with ALWIP mode.    -   i. In one example, X may depend on the block dimensions, such as        width and/or height.

7. It is proposed to remove the storage of ALWIP flag from line buffer.

-   a. In one example, when the 2^(nd) block to be accessed is located    in a different LCU/CTU row/region compared to the current block, the    conditional check of whether the 2^(nd) block is coded with ALWIP is    skipped.-   b. In one example, when the 2^(nd) block to be accessed is located    in a different LCU/CTU row/region compared to the current block, the    2^(nd) block is treated in the same way as non-ALWIP mode, such as    treated as normal intra coded block.

8. When encoding the ALWIP flag, no more than K (K >= 0) contexts may beused.

-   a. In one example, K = 1.

9. It is proposed to store the converted intra prediction mode of ALWIPcoded blocks instead of directly storing the mode index associated withthe ALWIP mode.

-   a. In one example, the decoded mode index associated with one ALWIP    coded block is mapped to the normal intra mode, such as according to    map_alwip_to_angular as described in Section 2.5.7.-   b. Alternatively, furthermore, the storage of ALWIP flag is totally    removed.-   c. Alternatively, furthermore, the storage of ALWIP mode is totally    removed.-   d. Alternatively, furthermore, condition check of whether one    neighboring/current block is coded with ALWIP flag may be skipped.-   e. Alternatively, furthermore, the conversion of modes assigned for    ALWIP coded blocks and normal intra predictions associated with one    accessed block may be skipped.

ALWIP on Different Color Components

10. It is proposed that an inferred chroma intra mode (e.g., DM mode)might be always applied if the corresponding luma block is coded withALWIP mode.

-   a. In one example, chroma intra mode is inferred to be DM mode    without signaling if the corresponding luma block is coded with    ALWIP mode.-   b. In one example, the corresponding luma block may be the one    covering the corresponding sample of a chroma sample located at a    given position (e.g., top-left of current chroma block, center of    current chroma block).-   c. In one example, the DM mode may be derived according to the intra    prediction mode of the corresponding luma block, such as via mapping    the (ALWIP) mode to one of the normal intra mode.

11. When the corresponding luma block of the chroma blocks is coded withALWIP mode, several DM modes may be derived.

12. It is proposed that a special mode is assigned to the chroma blocksif one corresponding luma block is coded with ALWIP mode.

-   a. In one example, the special mode is defined to be a given normal    intra prediction mode regardless the intra prediction mode    associated with the ALWIP coded blocks.-   b. In one example, different ways of intra prediction may be    assigned to this special mode.

13. It is proposed that ALWIP may also be applied to chroma components.

-   a. In one example, the matrix and/or bias vector may be different    for different color components.-   b. In one example, the matrix and/or bias vector may be predefined    jointly for blue chroma difference (Cb) and red difference chroma    (Cr).    -   i. In one example, Cb and Cr component may be concatenated.    -   ii. In one example, Cb and Cr component may be interleaved.-   c. In one example, the chroma component may share the same ALWIP    intra-prediction mode as the corresponding luma block.    -   i. In one example, the same ALWIP intra-prediction mode is        applied on the chroma component if the corresponding luma block        applies the ALWIP mode and the chroma block is coded with DM        mode.    -   ii. In one example, the same ALWIP intra-prediction mode is        applied on the chroma component and the linear interpolation        thereafter can be skipped.    -   iii. In one example, the same ALWIP intra-prediction mode is        applied on the chroma component with a subsampled matrix and/or        bias vector.

    d. In one example, the number of ALWIP intra-prediction modes for    different component may be different.    -   i. For example, the number of ALWIP intra-prediction modes for        chroma components may be less than that for luma component for        the same block width and height.

Applicability of ALWIP

14. It is proposed that whether ALWIP can be applied may be signaled.

-   a. For example, it may be signaled at sequence level (e.g., in    sequence parameter set (SPS)), at picture level (e.g., in picture    parameter set (PPS) or picture header), at slice level (e.g. in    slice header), at tile group level (e.g., in tile group header), at    tile level, at CTU row level, or at CTU level.-   b. For example, intra_lwip_flag may not be signaled and inferred to    be 0 if ALWIP cannot be applied.

15. It is proposed that whether ALWIP can be applied may depend on theblock width (W) and/or height (H).

-   c. For example, ALWIP may not be applied if W>=T1 (or W>T1) and    H>=T2 (or H> T2). E.g., T1=T2=32;    -   i. For example, ALWIP may not be applied if W<=T1 (or W<T1) and        H<=T2 (or H< T2). E.g., T1=T2=32;-   d. For example, ALWIP may not be applied if W>=T1 (or W>T1) or H>=T2    (or H> T2). E.g., T1=T2=32;    -   i. For example, ALWIP may not be applied if W<=T1 (or W<T1) or        H<=T2 (or H< T2). E.g., T1=T2=32;-   e. For example, ALWIP may not be applied if W + H>=T (or W * H> T).    E.g., T = 256;    -   i. For example, ALWIP may not be applied if W + H<=T (or W + H<        T). E.g., T = 256;-   f. For example, ALWIP may not be applied if W * H>=T (or W * H> T).    E.g., T = 256;    -   i. For example, ALWIP may not be applied if W * H<=T (or W * H<        T). E.g., T = 256;

    g. For example, intra_lwip_flag may not be signaled and inferred to    be 0 if ALWIP cannot be applied.

Calculation Problems in ALWIP

16. It is proposed that any shift operation involved in ALWIP can onlyleft shift or right shift a number by S, where S must be larger or equalto 0.

-   a. In one example, the right shift operation may be different when S    is equal to 0 or larger than 0.    -   i. In one example, upsBdryX[ x ] should be calculated as    -   $\begin{array}{l}        {\text{upsBdryX}\left\lbrack {\mspace{6mu}\text{x}\mspace{6mu}} \right\rbrack = \mspace{6mu}\left( {\mspace{6mu}{\sum_{\text{i}\mspace{6mu}\text{=}\mspace{6mu}\text{0}}^{\text{uDwn} - \text{1}}{\text{refX}\left\lbrack {\mspace{6mu}\text{x}\mspace{6mu} \ast \mspace{6mu}\text{uDwn} + \text{i}} \right\rbrack}}\mspace{6mu} +} \right)} \\        {\left( {\mspace{6mu} 1\mspace{6mu} \ll \left( {\mspace{6mu}\text{Log2}\left( {\mspace{6mu}\text{uDwn}} \right) - (1)\mspace{6mu}} \right)} \right)\mspace{6mu}} \\        {\gg \mspace{6mu}\text{Log2}\left( {\mspace{6mu}\text{uDwn}\mspace{6mu}} \right)\mspace{6mu}\text{when}\mspace{6mu}\text{uDwn>1,}\mspace{6mu}\text{and}} \\        {\text{upsBdryX}\left\lbrack {\mspace{6mu}\text{x}\mspace{6mu}} \right\rbrack\mspace{6mu}{\sum_{\text{i}\mspace{6mu}\text{=}\mspace{6mu}\text{0}}^{\text{uDwn} - \text{1}}{\text{refX}\left\lbrack {\mspace{6mu}\text{x}\mspace{6mu} \ast \mspace{6mu}\text{uDwn} + \text{i}} \right\rbrack\mspace{6mu}}}} \\        {\text{when}\mspace{6mu}\text{uDwn is equal to 1}\text{.}}        \end{array}$-   b. In one example, upsBdryX[ x ] should be calculated as-   $\begin{array}{l}    {\text{upsBdryX}\left\lbrack {\mspace{6mu}\text{x}\mspace{6mu}} \right\rbrack = \left( {\mspace{6mu}{\sum_{\text{i}\mspace{6mu}\text{=}\mspace{6mu}\text{0}}^{\text{uDwn} - \text{1}}{\text{refX}\left\lbrack {\mspace{6mu}\text{x}\mspace{6mu} \ast \mspace{6mu}\text{uDwn}\mspace{6mu}\text{+}\mspace{6mu}\text{i}\mspace{6mu}} \right\rbrack\mspace{6mu} +}}} \right)} \\    {\left( {\mspace{6mu} 1\mspace{6mu} \ll \mspace{6mu}\text{Log2}\left( {\mspace{6mu}\text{uDwn}\mspace{6mu}} \right)\mspace{6mu} \gg (1)\mspace{6mu}} \right)\mspace{6mu} \gg \mspace{6mu}\text{Log2}\left( {\mspace{6mu}\text{uDwn}\mspace{6mu}} \right)}    \end{array}$

17. It is proposed that the results should be rounded toward-zero oraway-from-zero in the up-sampling process of ALWIP.

-   a. In one example,-   $\begin{array}{l}    {\text{predSamples}\left\lbrack {\mspace{6mu}\text{xHor}\mspace{6mu}\text{+}\mspace{6mu}\text{dX}\mspace{6mu}} \right\rbrack\left\lbrack {\mspace{6mu}\text{yHor}\mspace{6mu}} \right\rbrack =} \\    \left( {\mspace{6mu}\left( {\mspace{6mu}\text{upHor} - \text{dX}\mspace{6mu}} \right) \ast \mspace{6mu}\text{predSamples}\left\lbrack {\mspace{6mu}\text{xHor}\mspace{6mu}} \right\rbrack\left\lbrack {\mspace{6mu}\text{yHor}\mspace{6mu}} \right\rbrack} \right) \\    {+ \mspace{6mu}\text{dX}\mspace{6mu} \ast \mspace{6mu}\text{predSamples}\left\lbrack {\mspace{6mu}\text{xHor}\mspace{6mu}\text{+}\mspace{6mu}\text{upHor}\mspace{6mu}} \right\rbrack\left\lbrack {\mspace{6mu}\text{yHor}\mspace{6mu}} \right\rbrack +} \\    {\left( \text{offsetHor} \right)\mspace{6mu}/\mspace{6mu}\text{upHor}\mspace{6mu}\mspace{6mu}\mspace{6mu}\mspace{6mu}\mspace{6mu}\mspace{6mu}\mspace{6mu}\mspace{6mu}\mspace{6mu}\mspace{6mu}\left( {8 - \text{X39}} \right)}    \end{array}$-   and-   $\begin{array}{l}    {\text{predSamples}\left\lbrack {\mspace{6mu}\text{xVer}\mspace{6mu}} \right\rbrack\left\lbrack {\mspace{6mu}\text{yVer}\mspace{6mu}\text{+}\mspace{6mu}\text{dY}\mspace{6mu}} \right\rbrack =} \\    {\left( {\mspace{6mu}\left( {\mspace{6mu}\text{upVer} - \text{dY}} \right)} \right) \ast \mspace{6mu}\text{predSamples}\left\lbrack {\mspace{6mu}\text{xVer}\mspace{6mu}} \right\rbrack\left\lbrack {\mspace{6mu}\text{yVer}\mspace{6mu}} \right\rbrack\mspace{6mu} +} \\    {\text{dY}\mspace{6mu} \ast \mspace{6mu}\text{predSamples}\left\lbrack {\mspace{6mu}\text{xVer}\mspace{6mu}} \right\rbrack\left\lbrack {\mspace{6mu}\text{yVer}\mspace{6mu}\text{+}\mspace{6mu}\text{upVer}\mspace{6mu}} \right\rbrack + \left( {\text{offsetVer}\mspace{6mu}} \right)\mspace{6mu}/} \\    {\text{upVer}\mspace{6mu}\mspace{6mu}\mspace{6mu}\mspace{6mu}\mspace{6mu}\mspace{6mu}\mspace{6mu}\mspace{6mu}\mspace{6mu}\mspace{6mu}\mspace{6mu}\mspace{6mu}\mspace{6mu}\left( {8 - \text{X40}} \right)}    \end{array}$

where offsetHor and offsetVer are integers. For example, offsetHor =upHor/2 and offsetVer=upVer/2. Interaction with Other Coding Tools

18. It is proposed that ALWIP may be used for a CIIP-coded block.

-   a. In one example, in a combination of intra and inter prediction    (CIIP)-coded block, it may be explicitly signaled whether an ALWIP    intra-prediction mode or a normal intra prediction mode such as    Planar is used to generate the intra prediction signal.-   b. In one example, it may be implicitly inferred whether an ALWIP    intra-prediction mode or a normal intra prediction mode such as    Planar may be used to generate the intra prediction signal.    -   i. In one example, ALWIP intra-prediction mode may never be used        in a CIIP coded block. 1) Alternatively, normal intra prediction        may never be used in a CIIP coded block.    -   ii. In one example, it may be inferred from information of        neighboring blocks whether an ALWIP intra-prediction mode or a        normal intra prediction mode such as Planar is used to generate        the intra prediction signal.

19. It is proposed that the whole or partial of the procedure used todown-sample the neighboring luma samples in the CCLM mode may be used todown-sample the neighboring samples in the ALWIP mode.

-   a. Alternatively, the whole or partial of the procedure used to    down-sample the neighboring luma samples in the ALWIP mode may be    used to down-sample the neighboring samples in the CCLM mode.-   b. The down-sampling procedure may be invoked with different    parameters/arguments when it is used in the CCLM process and ALWIP    process.-   c. In one example, the down-sampling method (such as selection of    neighboring luma locations, down-sampling filters) in the CCLM    process may be utilized in the ALWIP process.-   d. The procedure used to down-sample the neighboring luma samples at    least include the selection of down-sampled positions, the    down-sampling filters, the rounding and clipping operations.

20. It is proposed that a block coded with ALWIP mode cannot apply RSTor/and secondary transform or/and rotation transform or/andNon-Separable Secondary Transform (NSST).

-   a. In one example, whether such constraint may be applied or not may    depend on the dimension information of the block, e.g., same as    conditions described in (15).-   b. Alternatively, ALWIP mode may be disallowed when RST or/and    secondary transform or/and rotation transform or/and Non-separable    secondary transforms (NSST) is applied.-   c. Alternatively, a block coded with ALWIP mode may apply RST or/and    secondary transform or/and rotation transform or/and NSST.    -   i. In one example, the selection of transform matrix may depend        the ALWIP intra-prediction mode.    -   ii. In one example, the selection of transform matrix may depend        the normal intra-prediction mode which is converted from the        ALWIP intra-prediction mode.    -   iii. In one example, the selection of transform matrix may        depend the classification on the normal intra-prediction mode        which is converted from the ALWIP intra-prediction mode.

21. It is proposed that a block coded with ALWIP mode cannot applyBlock-based DPCM (BDPCM) or Residue DPCM (RDPCM).

-   a. Alternatively, ALWIP mode may be disallowed when BDPCM or RDPCM    is applied.

22. It is proposed that a block coded with ALWIP mode may only useDCT-II as the transform.

-   a. In one example, the signalling of transform matrix indices is    always skipped.-   b. Alternatively, it is proposed that the transform used for a block    coded with ALWIP mode may be implicitly derived instead of    explicitly signaled. For example, the transform may be selected    following the way proposed in JVET-M0303.-   c. Alternatively, it is proposed that a block coded with ALWIP mode    may only use transform skip.    -   i. Alternatively, furthermore, when ALWIP is used, the        signalling of indication of usage of transform skip is skipped.-   d. In one example, ALWIP mode information (such as enabled/disabled,    prediction mode index) may be conditionally signalled after    indications of transform matrix.    -   i. In one example, for a given transform matrix (such as        transform skip or DCT-II), the indications of ALWIP mode        information may be signalled.    -   ii. Alternatively, furthermore, the indications of ALWIP mode        information may be skipped for some pre-defined transform        matrices.

23. It is proposed that a block coded with ALWIP mode is regarded to becoded with a normal intra-prediction converted from the ALWIPintra-prediction mode when the selected transform is mode-dependent.

24. ALWIP mode may not use transform skip.

-   a. For example, there is no need to further signal the indication of    usage of transform skip in this case.-   b. Alternatively, ALWIP mode may be disallowed when transform skip    is applied.    -   i. For example, there is no need to signal ALWIP mode        information when transform skip is applied in this case.

25. In the filtering process, such as deblocking filter, sample adaptiveoffset (SAO), adaptive loop filter (ALF), how to select the filtersand/or whether to filter samples may be determined by the usage ofALWIP.

26. Unfiltered neighboring samples may be used in ALWIP mode.

-   a. Alternatively, filtered neighboring samples may be used in ALWIP    mode.-   b. In one example, filtered neighboring samples may be used for down    sampling and unfiltered neighboring samples may be used for up    sampling.-   c. In one example, unfiltered neighboring samples may be used for    down sampling and filtered neighboring samples may be used for up    sampling.-   d. In one example, filtered left neighboring samples may be used in    up sampling and unfiltered above neighboring samples may be used in    up sampling.-   e. In one example, unfiltered left neighboring samples may be used    in up sampling and filtered above neighboring samples may be used in    up sampling.-   f. In one example, whether filter or unfiltered neighboring samples    is used may depend on the ALWIP mode.    -   i. In one example, ALWIP mode may be converted to traditional        intra prediction mode, and whether filtered or unfiltered        neighboring samples is used may depend on the converted        traditional intra prediction mode. For example, such decision is        same as traditional intra prediction modes.    -   ii. Alternatively, whether filter or unfiltered neighboring        samples is used for ALWIP mode may be signaled.-   g. In one example, the filtered samples may be generated same as    traditional intra prediction modes.

27. Which matrices or/and offset vectors are used may depend onreshaping (a.k.a., LMCS, luma mapping with chroma scaling) information.

-   a. In one example, different matrices or/and offset vectors may be    used when reshaping is on and off.-   b. In one example, different matrices or/and offset vectors may be    used for different reshaping parameters.-   c. In one example, ALWIP may be always performed in original domain.    -   i. For example, neighboring sample are mapped to the original        domain (if reshaping is applied) before used in ALWIP.

28. ALWIP may be disabled when reshaping is applied.

-   a. Alternatively, reshaping may be disabled when ALWIP is enabled.-   b. In one example, ALWIP may be disabled for HDR (high dynamic    range) content when reshaping is applied.

29. The matrices used in ALWIP may depend on sample bit-depth.

-   a. Alternatively, furthermore, the offset values used in ALWIP may    depend on sample bit-depth.-   b. Alternatively, the matrix parameters and offset values can be    stored in M-bit precision for N-bit samples (M<=N), e.g., the matrix    parameters and offset values can be stored in 8-bit precision for a    10-bit sample.-   c. The sample bit-depth may be the bit-depth of input array for a    color component such as luma.-   d. The sample bit-depth may be the bit-depth of internal    array/reconstructed sample for a color component, such as luma.

30. The matrix parameters and/or offset values for a specified blocksize may be derived from the matrix parameters and/or offset values forother block sizes.

31. In one example, the 16×8 matrix of 8×8 block can be derived from the16×4 matrix of 4×4 block.

32. It is proposed that the prediction generated by ALWIP may be treatedas an intermedium or intermediate signal which will be processed toobtain the prediction signal to be further used.

-   a. In one example, Position Dependent Intra Prediction Combination    (PDPC) may be applied on the prediction generated by ALWIP to    generate the prediction signal to be further used.    -   i. In one example, PDPC is done on an ALWIP coded block in the        same way as the block is coded with a specific normal        intra-prediction mode, such as Planar or DC.    -   ii. In one example, PDPC is done on an ALWIP coded block in the        same way as the block coded with a normal intra-prediction mode        which is converted from the ALWIP intra-prediction mode.    -   iii. In one example, PDPC is applied on an ALWIP coded block        conditionally.        -   1) For example, PDPC is applied on an ALWIP coded block only            when PDPC is applied on the normal intra-prediction mode            which is converted from the ALWIP intra-prediction mode.-   b. In one example, the boundary samples prediction generated by    ALWIP may be filtered with neighbouring samples to generate the    prediction signal to be further used.    -   i. In one example, filtering on boundary samples is done on an        ALWIP coded block in the same way as the block is coded with a        specific normal intra-prediction mode, such as Planar or DC.    -   ii. In one example, filtering on boundary samples is done on an        ALWIP coded block in the same way as the block coded with a        normal intra-prediction mode which is converted from the ALWIP        intra-prediction mode.    -   iii. In one example, filtering on boundary samples is applied on        an ALWIP coded block conditionally.        -   1) For example, filtering on boundary samples is applied on            an ALWIP coded block only when filtering on boundary samples            is applied on the normal intra-prediction mode which is            converted from the ALWIP intra-prediction mode.

33. It is proposed that interpolation filters other than bilinearinterpolation filter may be used in the up-sampling process of ALWIP.

-   a. In one example, 4-tap interpolation filters may be used in the    up-sampling process of ALWIP.    -   i. For example, the 4-tap interpolation filters in VVC used to        do the motion compensation for chroma components may be used in        the up-sampling process of ALWIP.    -   ii. For example, the 4-tap interpolation filters in VVC used to        do angular intra-prediction may be used in the up-sampling        process of ALWIP.    -   iii. For example, the 8-tap interpolation filters in VVC used to        do the motion compensation for luma component may be used in the        up-sampling process of ALWIP.

34. Samples within a block coded in ALWIP mode may be predicted indifferent ways.

-   a. In one example, for a W*H block, prediction of a sW*sH sub-block    within it may be generated by applying sW*sH ALWIP to it.    -   i. In one example, for a W*H block, prediction of its top-left        W/2*H/2 block may be generated by applying W/2*H/2 ALWIP to it.    -   ii. In one example, for a W*H block, prediction of its left        W/2*H block may be generated by applying W/2*H ALWIP to it.    -   iii. In one example, for a W*H block, prediction of its top        W*H/2 block may be generated by applying W*H/2 ALWIP to it.    -   iv. In one example, the sW*sH sub-block may have available left        or/and above neighboring samples.-   b. In one example, how to decide the position of the sub-block may    depend on dimension of the block.    -   i. For example, when W >= H, prediction of its left W/2*H block        may be generated by applying W/2*H ALWIP to it.    -   ii. For example, when H >= W, prediction of its top W*H/2 block        may be generated by applying W*H/2 ALWIP to it.    -   iii. For example, when W is equal to H, prediction of its        top-left W/2*H/2 block may be generated by applying W/2*H/2        ALWIP to it.-   c. In one example, furthermore, prediction of the remaining samples    (e.g., samples do not belong to the sW*sH sub-block) may be    generated by applying the W*H ALWIP.    -   i. Alternatively, prediction of the remaining samples may be        generated by applying conventional intra prediction (e.g., using        the converted intra prediction mode as the intra mode).    -   ii. Furthermore, calculation may be skipped for samples in the        sW*sH sub-block.

35. Samples within a block coded in ALWIP mode may be predicted insub-block (e.g., with size sW*sH) level.

-   a. In one example, sW*sH ALWIP may be applied to each sub-block    using neighboring reconstructed samples (e.g., for boundary    sub-blocks) or/and neighboring predicted samples (e.g., for inner    sub-blocks).-   b. In one example, sub-blocks may be predicted in raster-scan order.-   c. In one example, sub-blocks may be predicted in zigzag order.-   d. In one example, width (height) of sub-blocks may be no larger    than sWMax (sHMax).-   e. In one example, when a block with either width or height or both    width and height are both larger than (or equal to) a threshold L,    the block may be split into multiple sub-blocks.-   f. The threshold L may be pre-defined or signaled in    SPS/PPS/picture/slice/tile group/tile level.    -   i. Alternatively, the thresholds may depend on certain coded        information, such as block size, picture type, temporal layer        index, etc. al.

36. It is proposed that the neighbouring samples (adjacent ornon-adjacent) are filtered before being used in ALWIP.

-   a. Alternatively, neighbouring samples are not filtered before being    used in ALWIP.-   b. Alternatively, neighbouring samples are conditionally filtered    before being used in ALWIP.    -   i. For example, neighbouring samples are filtered before being        used in ALWIP only when the ALWIP intra-prediction mode is equal        to one or some specific values.

37. It is proposed that when coding the ALWIP flag, the method to derivethe context for the ALWIP flag in arithmetic coding is the same for alldimensions of the current block.

-   a. In one example, the method to derive the context for the ALWIP    flag in arithmetic coding is the same when (Abs(Log2(cbWidth) -    Log2(cbHeight) ) is larger than 1 or not, where CbWidth and CbHeight    are the width and height of the current block, respectively.-   b. In one example, the derivation of the context for the ALWIP flag    in arithmetic coding only depends on neighboring blocks' ALWIP    information and/or the availability of the neighbouring blocks.    -   i. In one example, multiple neighboring blocks ALWIP information        (e.g., intra_lwip_flag) and/or the availability of the        neighbouring blocks are directly used. For example, the left and        above neighbouring blocks' ALWIP flags and/or the availability        of the left and neighbouring blocks are used to derive the        context for the ALWIP flag in arithmetic coding. An example is        shown in Table 2. Alternatively, furthermore, the context index        offset ctxInc = ( condL && availableL) + (condA && availableA) +        ctxSetIdx * 3.

Table 2 Specification of ctxInc using left and above syntax elementsSyntax element condL condA ctxSetI dx intra_lwip_flag[ x 0 ][ y0 ]intra_lwip_flag[ xNbL ][ yNbL ] intra_lwip_flag[ xNbA ][ yNbA ] 0

-   ii. In one example, one of the neighboring block’s ALWIP information    (e.g., intra_lwip_flag) is used to derive the context for the ALWIP    flag in arithmetic coding, and the neighbouring block may be the    left neighbouring block. An example is shown in Table 3.    Alternatively, furthermore, the context index offset ctxInc = (    condL && availableL ) + ctxSetIdx * 3.

Table 3 Specification of ctxInc using left and above syntax elementsSyntax element condL condA ctxSetI dx intra_lwip_flag[ x 0 ][ y0 ]intra_lwip_flag[ xNbL ][ yNbL ] 0

-   iii. In one example, one of the neighboring block’s ALWIP flag    information (e.g., intra_lwip_flag) is used to derive the context    for the ALWIP flag in arithmetic coding, and the neighbouring block    may be the above neighbouring block.. An example is shown in    Table 4. Alternatively, furthermore, the context index offset ctxInc    = ( condA && availableA) + ctxSetIdx * 3.

Table 4 Specification of ctxInc using left and above syntax elementsSyntax element condL condA ctxSetI dx intra_lwip_flag[ x 0 ][ y0 ]intra_lwip_flag[ xNbA ][ yNbA ] 0

-   c. In one example, one fixed context is used for coding the ALWIP    flag in arithmetic coding.-   d. In one example, ALWIP flag is bypass coded in arithmetic coding.-   e. Alternatively, K contexts may be used for coding ALWIP flag in    arithmetic coding. The context to be used may depend on dimension    (e.g., width denoted as W and height denoted as H) of the block.    -   i. In one example, K is equal to 2. When W > N * H or H > N * W        (e.g., N = 2), the first context is used, otherwise, the second        context is used.

-   38. It is proposed that N (N >= 0) contexts may be used to code the    ALWIP flag (e.g., intra_lwip_flag) in arithmetic coding.    -   a. In one example, N is equal to three. ALWIP flag and/or        availability of two neighboring or/and non-adjacent blocks may        be used for deriving the used context for the ALWIP flag in        arithmetic coding.        -   i. In one example, the two neighboring blocks may include            the above (e.g., B1 in FIG. 10 ) block and the left (e.g.,            A1 in FIG. 10 ) block.        -   ii. In one example, the two neighboring blocks may include            the above block and the below-left (e.g., A2 in FIG. 10 )            block.        -   iii. In one example, the two neighboring blocks may include            the above block and the above-right (e.g., B2 in FIG. 10 )            block.        -   iv. In one example, the two neighboring blocks may include            the above-right (e.g., B2 in FIG. 10 ) block and the left            (e.g., A1 in FIG. 10 ) block.        -   v. In one example, the two neighboring blocks may include            the above-right (e.g., B2 in FIG. 10 ) block and the            below-left (e.g., A2 in FIG. 10 ) block.        -   vi. In one example, the two neighboring blocks may include            the left block (e.g., A1 in FIG. 10 ) and the below-left            (e.g., A2 in FIG. 10 ) block.        -   vii. In one example, the neighboring block may be defined            differently from FIG. 10 . an example is described in FIG.            16 . The two neighboring blocks may include any two of the            {above-right, above, above-left, left, below-left} blocks.            E.g., The two neighboring blocks may include any two of the            blocks in {B0, B1, B2, A0, A1 }.    -   b. In one example, N is equal to two. ALWIP flag and/or        availability of one neighboring or/and non-adjacent block may be        used for deriving the used context for the ALWIP flag in        arithmetic coding.        -   i. In one example, the neighboring block may be anyone of            the {above-right, above, above-left, left, below-left}. An            example of the neighboring block is described in FIG. 10 .        -   ii. In one example, the neighboring block may be anyone of            the {above-right, above, above-left, left, below-left}            block. An example of the neighboring block is described in            FIG. 16 .    -   c. In one example, one fixed context may be used for coding        ALWIP flag in arithmetic coding.    -   d. In one example, ALWIP flag may be bypass coded in arithmetic        coding. FIG. 16 shows an example of neighboring blocks.-   39. It is proposed that the reduced boundary samples may be    generated without calculating the up-sampling boundary samples.    -   a. In one example, the reference samples located at the        upsampling boundary sample positions are directly used for the        prediction upsampling process.        -   i. In one example, the upsampling boundary samples may not            be computed by averaging multiple adjacent reference            samples.    -   b. In one example, the reduced boundary samples may be directly        calculated from reference samples and the downscaling factor.        -   i. In one example, the downscaling factor may be computed by            the transform block size and the downsampled boundary size.-   40. In one example, the samples may be with different precisions in    different filtering stages in the up-sampling process in ALWIP.    “Samples” may refer to prediction samples or any intermedium samples    before or after the up-sampling process.    -   a. In one example, samples are up-sampled along a first        dimension horizontally in a first filtering stage; then samples        are up-sampled along a second dimension vertically in a second        filtering stage in the up-sampling process in ALWIP.        -   i. Alternatively, samples are up-sampled along a first            dimension vertically in a first filtering stage; then            samples are up-sampled along a second dimension horizontally            in a second filtering stage in the up-sampling process in            ALWIP.    -   b. In one example, the output up-sampling results without        right-shifting or division in the first filtering stage may be        used as the input samples to the second filtering stage.        -   i. In one example, the output up-sampling filtering results            in the second filtering stage may be right-shifted by Shift1            or divided by Dem1 to derive the final up-sampled results.        -   ii. In one example, the output up-sampling filtering results            in the first filtering stage may be right-shifted by Shift2            or divided by Dem2 to derive the final up-sampled results.            -   1) In one example, Shift1=2 ×Shift2; Dem1= Dem2 ×Dem2.        -   iii. In one example, the samples, which are input to the            second filtering stage but are not the output up-sampling            results in the first filtering stage, may be left-shifted            Shift3 or multiplied by Dem3 before being input to the            second filtering stage.            -   1) In one example, Shift3 = Shift1; Dem3 = Dem2.

        c. In one example, the output up-sampling results in the first        filtering stage may be right-shifted by Shift1 or divided by        Dem1 before being used as the input samples to the second        filtering stage.        -   i. In one example, the output up-sampling filtering results            in the second filtering stage may be right-shifted by Shift2            or divided by Dem2 to derive the final up-sampled results,            where Shift2 may be not equal to Shift1, e.g. Shift2 >            Shift1; Dem2 may be not equal to Dem1, e.g. Dem2 > Dem1 .        -   ii. In one example, the output up-sampling filtering results            in the first filtering stage may be right-shifted by Shift3            or divided by Dem3 to derive the final up-sampled results,            where Shift3 may be equal to Shift1; Dem3 maybe not equal to            Dem1 .            -   1) In one example, Shift3=Shift1+Shift2.        -   iii. In one example, the samples, which are input to the            second filtering stage but are not the output up-sampling            results in the first filtering stage, may be left-shifted or            multiplied by a factor before being input to the second            filtering stage.    -   d. In one example, the output up-sampling results in the first        filtering stage may be left-shifted by Shift1 or multiplied by        Dem1 before being used as the input samples to the second        filtering stage.        -   i. In one example, the output up-sampling filtering results            in the second filtering stage may be right-shifted or            divided by a factor to derive the final up-sampled results.        -   ii. In one example, the output up-sampling filtering results            in the first filtering stage may be right-shifted or divided            by a factor to derive the final up-sampled results.        -   iii. In one example, the samples, which are input to the            second filtering stage but are not the output up-sampling            results in the first filtering stage, may be left-shifted by            Shift2 or multiplied by Dem2 before being input to the            second filtering stage, where Shift2 may be not equal to            Shift1, e.g. Shift2 > Shift1; Dem1 may be not equal to Dem2,            e.g. Dem2 > Dem1 .    -   e. In one example, the samples which are input to the first        filtering stage may be left-shifted by Shift1 or multiplied by        Dem1 before being used as the input samples to the first        filtering stage.        -   i. In one example, the output up-sampling filtering results            in the second filtering stage may be right-shifted or            divided by a factor to derive the final up-sampled results.        -   ii. In one example, the output up-sampling filtering results            in the first filtering stage may be right-shifted or divided            by a factor to derive the final up-sampled results.        -   iii. In one example, the samples, which are input to the            second filtering stage but are not the output up-sampling            results in the first filtering stage, may be left-shifted by            Shift2 or multiplied by Dem2 before being input to the            second filtering stage, where Shift2 may be not equal to            Shift1, e.g. Shift2 > Shift1; Dem2 may be not equal to Dem1,            e.g. Dem2 > Dem1 .

5. Embodiments

Newly added parts are highlighted in bold faced italics and deletedparts are highlighted in underline italicized text.

5.1 One Example

Three contexts are used for coding ALWIP flag.

Table 9-15 Assignment of ctxInc to syntax elements with context codedbins Syntax element binIdx 0 1 2 3 4 >= 5 ... terminate na na na na naintra_lwip_flag[ ][ ] (Abs( Log2(cbWid th) -Log2(cbHeight) ) > 1) ? 3 :( 0,1,2 (clause 9.5.4.2.2) ) na na na na na intra_lwip_flag[ ][ ] (0,1,2 (clause 9.5.4.2.2) ) na na na na na

Table 9-15 Assignment of ctxInc to syntax elements with context codedbins Syntax element binIdx 0 1 2 3 4 >= 5 intra_lwip_mpm_flag[ ][ ] 0 nana na na na intra_lwip_mpm_idx[ ][ ] bypass bypass na na na naintra_lwip_mpm_rem ainder[ ][ ] bypass bypass bypass bypass bypass na

5.2 One Example

One fixed context is used for coding ALWIP flag.

Table 9-15 Assignment of ctxInc to syntax elements with context codedbins Syntax element binIdx 0 1 2 3 4 >= 5 ... terminate na na na na naintra_lwip_flag[ ][ ] (Abs(Log2(cbWid th) -Log2(cbHeight) ) > 1) ? 3 :(0,1,2 (clause 9.5.4.2.2) ) na na na na na intra_1wip_flag[ ] [ ] 0 nana na na na intra_lwip_mpm_flag[ ][ ] 0 na na na na naintra_lwip_mpm_idx[ ][ ] bypass bypass na na na na intra_lwip_mpm_remainder[ ][ ] bypass bypass bypass bypass bypass na

5.3 One Example

Perform the boundary reduction process in one-step.

Below embodiments are based on the adoptedJVET-N0220-proposal-test-CE3-4.1_v2.

8.4.4.2.X1 Affine linear weighted intra sample prediction8.4.4.2.X3Specification of the Boundary Reduction Process

Inputs to this process are:

-   a variable nTbX specifying the transform block size,-   reference samples refX[ x ] with x = 0..nTbX - 1,-   a variable boundarySize specifying the downsampled boundary size,-   a flag needUpsBdryX specifying whether intermediate boundary samples    are required for upsampling,-   a variable upsBdrySize specifying the boundary size for upsampling.

Outputs of this process are the reduced boundary samples redX[ x ] withx = 0..boundarySize - 1 and upsampling boundary samples upsBdryX[ x ]with x = 0..upsBdrySize - 1.

The upsampling boundary samples upsBdryX[ x ] with x = 0..upsBdrySize -1 are derived as follows:

-   If needUpsBdryX is equal to TRUE and upsBdrySize is less than nTbX,    the following applies:-   uDwn = nTbX / upsBdrySize-   upsBdryX[x]refX[x * uDwn]-   $\begin{matrix}    {upsBdryX\lbrack x\rbrack = ({\sum{{}_{i - 0}^{uDwn - 1}refX\left\lbrack {x \ast uDwn + 1} \right\rbrack +}}} \\    {\left( {1 \ll \left( {Log2\left( {uDwn - 1} \right)} \right)} \right) \gg Log2\left( {uDwn} \right)}    \end{matrix}$-   Otherwise (upsBdrySize is equal to nTbX), upsBdryX[ x ] is set equal    to refX[ x ].

The reduced boundary samples redX[ x ] with x = 0..boundarySize - 1 arederived as follows:

-   If boundarySize is less than upsBdrySize nTbX, the following    applies:    -   bDwn = upsBdrySize  nTbX/boundrySize    -   $\begin{array}{l}        {\text{redX}\left\lbrack \text{x} \right\rbrack = ({\sum{{}_{\text{i} = 1}^{\text{bDwn-1}}upsBdryX\,\text{refX}\left\lbrack {\text{x} \ast \text{bDWn+1}} \right\rbrack +}}} \\        {\left( {1 \ll \left( {\text{Log2}\left( \text{bDwn} \right) - 1} \right)} \right) \gg \text{Log2}\left( \text{bDwn} \right)}        \end{array}$

The term upsBdryX in Equation 8-X33 is deleted.

-   Otherwise (boundarySize is equal to upsBdrySize nTbX), redX[ x ] is    set equal to upsBdryX[ x ] refX [ x ] .

5.4 One Example

Derive prediction samples with different precisions in differentfiltering stages in the up-sampling process in ALWIP.

Below embodiments are based on the adoptedJVET-N0217-proposal-test-CE3-4.1_v2.

8.4.4.2.X4 Specification of the Prediction Upsampling Process

Inputs to this process are:

-   a variable predW specifying the input block width,-   a variable predH specifying the input block height,-   affine linear weighted samples predLwip[ x ][ y ], with x =    O..predW - 1, y = O..predH - 1,-   a variable nTbW specifying the transform block width,-   a variable nTbH specifying the transform block height,-   a variable upsBdryW specifying the upsampling boundary width,-   a variable upsBdryH specifying the upsampling boundary height,-   top upsampling boundary samples upsBdryT[ x ] with x = 0..upsBdryW -    1,-   left upsampling boundary samples upsBdryL[ x ] with x =    0..upsBdryH - 1.

Outputs of this process are the predicted samples predSamples[ x ][ y ],with x = O..nTbW - 1, y = O..nTbH - 1. The sparse predicted samplespredSamples[m][n] are derived from predLwip[ x ][ y ], with x =O..predW - 1, y = O..predH -1 as follows:

upHor=nTbW/predW

upVer = nTbH/predH

$\begin{array}{l}{\text{predSamples}\left\lbrack {\left( \text{x+1} \right)*\text{upHor} - \text{1}} \right\rbrack\left\lbrack {\left( {\text{y} + \text{1}} \right)*\text{upVer} - \text{1}} \right\rbrack =} \\{\text{predLwip}\left\lbrack \text{x} \right\rbrack\left\lbrack \text{y} \right\rbrack}\end{array}$

The top boundary samples upsBdryT[ x ] with x = 0..upsBdryW-1 areassigned to predSamples[m][-1] as follows:

predSamples[(x + 1) * (nTbw/upsBdryW) − 1][−1] = upsBdryT[x]

The left boundary samples upsBdryL[ y ] with y = 0..upsBdryH - 1 areassigned to predSamples[-1][n] as follows:

predSamples[1][(y + 1) * (nTbH/upsBdryH) − 1] − upsBdryL[y]

The predicted samples predSamples[ x ][ y ], with x = O..nTbW - 1, y =O..nTbH - 1 are derived as follows:

-   If nTbH is greater than nTbW, the following ordered steps apply:    -   1. When upHor is greater than 1, hoizontal upsampling for all        sparse positions (xHor, yHor) = (m * uphor-1, n* upver-1) with m        = O..predW - 1, n= l..predH is applied with dX = l..uphor-1 as        follows:    -   $\begin{array}{l}        {\text{predSamples}\left\lbrack {\text{xHor}\, + \,\text{dX}} \right\rbrack\left\lbrack \text{yHor} \right\rbrack = \text{((upHor} - \text{dX)}*} \\        {\text{predSamples}\left\lbrack \text{xHor} \right\rbrack\left\lbrack \text{yHor} \right\rbrack +} \\        {\text{dX}*\text{predSamples}\left\lbrack {\text{xHor} + \text{upHor}} \right\rbrack\left( \left\lbrack \text{yHor} \right\rbrack \right)\text{/}\underset{¯}{\text{upHor}}}        \end{array}$    -   2. Vertical upsampling for all sparse positions (xver, yver) =        (m, n* upver-1) with m = O..nTbW - 1, n= O..predH - 1 is applied        with dY = 1..upver-1 as follows:        -   If yVer is equal to -1, predsamples[ xVer ][ yVer ] =            predsamples[ xVer][ yVer ] « log2(upHor)        -   $\begin{array}{l}            {\text{predSamples}\left\lbrack \text{xVer} \right\rbrack\left\lbrack {\text{yVer} + \text{dY}} \right\rbrack =} \\            \left( {\left( {\text{upVer} - \text{dY}} \right)*\text{predSamples}\left\lbrack \text{xVer} \right\rbrack\left\lbrack \text{yVer} \right\rbrack +} \right) \\            {\left( {\text{dY}*\text{predSamples}\left\lbrack \text{xVer} \right\rbrack\left\lbrack {\text{yVer} + \text{upVer}} \right\rbrack} \right)/upVer +} \\            {\left( \left( {\text{1} \ll \left( {\text{log2}\left( \text{upHor} \right) + \text{log2}\left( \text{upVer} \right) - \text{1}} \right)} \right) \right) \gg}            \end{array}$        -   (log2(upHor) + log2(upVer))-   Otherwise, the following ordered steps apply:    -   1. When upveris greater than 1, vertical upsampling for all        sparse positions (xver, yver) = (m* upHor-1, n* upver- 1) with m        = 1..predW, n= O..predH - 1 is applied with dY = 1..upVer-1 as        specified in (8-X40) (8-X41).    -   $\begin{array}{l}        {\text{predSamples}\left\lbrack \text{xVer} \right\rbrack\left\lbrack {\text{yVer} + \text{dY}} \right\rbrack =} \\        {\text{((upVer-dy)}*\text{predSamples}\left\lbrack \text{xVer} \right\rbrack\left\lbrack \text{yVer} \right\rbrack +} \\        {\text{dY}*\text{predSamples}\left\lbrack \text{xVer} \right\rbrack\left\lbrack {\text{yVer} + \text{upVer}} \right\rbrack)}        \end{array}$    -   2. Horizontal upsampling for all sparse positions (xHor, yHor) =        (m * upHor-1, n) with m = O..predW - 1, n= O..nTbH - 1 is        applied with dX = 1..upHor-1 as specified in (8-X39) as follows.        -   If xHor is equal to -1, predsamples[ xHor][ yHor] =            predsamples[ xHor][ yHor] « log2(upVer)        -   $\begin{array}{l}            {\text{predSamples}\left\lbrack {\text{xHor} + \text{dX}} \right\rbrack\left\lbrack \text{yHor} \right\rbrack =} \\            \left( {\left( \text{upHor-dX} \right)*\text{predSamples}\left\lbrack \text{xHor} \right\rbrack\left\lbrack \text{yHor} \right\rbrack +} \right) \\            {\text{dX*predSamples}\left\lbrack {\text{xHor} + \text{upHor}} \right\rbrack\left\lbrack \text{yHor} \right\rbrack +} \\            {\left( \left( {\text{1} \ll \left( {\text{log2}\left( \text{upHor} \right) + \text{log2}\left( \text{upVer} \right) - 1} \right)} \right) \right) \gg \left( {\log 2\left( \text{upHor} \right)} \right)\text{+}}            \end{array}$        -   log2((upVer))

5.5 Examples Corresponding to Bullet 40

Suppose the block dimensions are WxH. Samples P(x, y) with x= Sx, Sx+Kx,Sx+2Kx, Sx+3Kx,..., y=Sy, Sy+Ky, Sy+2Ky, Sy+3Ky... are input to theup-sampling process to derive the up-sampled samples S(x, y) withx=0,1,2...W-1, y= 0, 1, 2,... H-1. Kx and Ky are step sizes along thehorizontal and vertical directions respectively. (Sx, Sy) is thestarting position.

Suppose 1-D up-sampling is done horizontally in the first stage and 1-Dup-sampling is done vertically in the second stage.

In one example, the output results in the first stage withoutright-shifting may be derived as

S’( Sx+Kx-1, Sy) = F1*P(Sx, Sy) + F2*P(Sx+Kx, Sy).

$\begin{array}{l}{\text{S'}\left( {\mspace{6mu}\text{Sx+Kx-1,}\mspace{6mu}\text{Sy+Ky}} \right)\mspace{6mu} = \mspace{6mu}\text{F1*P}\left( {\text{Sx,}\mspace{6mu}\text{Sy+Ky}} \right)\text{+F2*}} \\{\text{P}\left( {\text{Sx+Kx,}\mspace{6mu}\text{Sy+Ky}} \right).}\end{array}$

F1, F2 are coefficients for a 2-tap filter and F1+F2 = 2^(N).

Then an output result in the second stage may be derived as

$\begin{array}{l}{\text{S'}\left( {\mspace{6mu}\text{Sx+Kx-1,}\mspace{6mu}\text{Sy+1}} \right)\mspace{6mu} = \mspace{6mu}\text{F3*}\mspace{6mu}\text{S'}\left( {\mspace{6mu}\text{Sx+Kx-1, Sy}} \right) + \text{F4*}\mspace{6mu}} \\{\text{S'}\left( {\mspace{6mu}\text{Sx+Kx-1,}\mspace{6mu}\text{Sy+Ky}} \right).}\end{array}$

F3, F4 are coefficients for a 2-tap filter and F3+F4 = 2^(N).

Then the final up-sampled sample value may be derived as:

-   S( Sx+Kx-1, Sy+1) = Shift( S’( Sx+Kx-1, Sy+1), 2N);-   S( Sx+Kx-1, Sy) = Shift(S’ ( Sx+Kx-1, Sy), N);-   S( Sx+Kx-1, Sy+Ky) = Shift(S^(′) ( Sx+Kx-1, Sy+Ky), N);

The examples described above may be incorporated in the context of themethods described below, e.g., methods 1100-1400 and 2100-2400, whichmay be implemented at a video encoder and/or decoder.

FIG. 11 shows a flowchart of an exemplary method for video processing.The method 1100 includes, at step 1110, determining that a current videoblock is coded using an affine linear weighted intra prediction (ALWIP)mode.

The method 1100 includes, at step 1120, constructing, based on thedetermining, at least a portion of a most probable mode (MPM) list forthe ALWIP mode based on an at least a portion of an MPM list for anon-ALWIP intra mode.

The method 1100 includes, at step 1130, performing, based on the MPMlist for the ALWIP mode, a conversion between the current video blockand a bitstream representation of the current video block.

In some embodiments, a size of the MPM list of the ALWIP mode isidentical to a size of the MPM list for the non-ALWIP intra mode. In anexample, the size of the MPM list of the ALWIP mode is 6.

In some embodiments, the method 1100 further comprises the step ofinserting default modes to the MPM list for the ALWIP mode. In anexample, the default modes are inserted prior to the portion of a MPMlist for the ALWIP mode that is based on the MPM list for the non-ALWIPintra mode. In another example, the default modes are insertedsubsequent to the portion of a MPM list for the ALWIP mode that is basedon the MPM list for the non-ALWIP intra mode. In yet another example,the default modes are inserted in an interleaved manner with the portionof a MPM list for the ALWIP mode that is based on the MPM list for thenon-ALWIP intra mode.

In some embodiments, constructing the MPM list for the ALWIP mode andthe MPM list for the non-ALWIP intra mode is based on one or moreneighboring blocks.

In some embodiments, constructing the MPM list for the ALWIP mode andthe MPM list for the non-ALWIP intra mode is based a height or a widthof the current video block.

In some embodiments, constructing the MPM list for the ALWIP mode isbased on a first set of parameters that is different from a second setof parameters used to construct the MPM list for the non-ALWIP intramode.

In some embodiments, the method 1100 further includes the step ofdetermining that a neighboring block of the current video block has beencoded with the ALWIP mode, and designating, in constructing the MPM listfor the non-ALWIP intra mode, the neighboring block as unavailable.

In some embodiments, the method 1100 further includes the step ofdetermining that a neighboring block of the current video block has beencoded with the non-ALWIP intra mode, and designating, in constructingthe MPM list for the ALWIP mode, the neighboring block as unavailable.

In some embodiments, the non-ALWIP intra mode is based on a normal intramode, a multiple reference line (MRL) intra prediction mode or an intrasub-partition (ISP) tool.

FIG. 12 shows a flowchart of an exemplary method for video processing.The method 1200 includes, at step 1210, determining that a lumacomponent of a current video block is coded using an affine linearweighted intra prediction (ALWIP) mode.

The method 1200 includes, at step 1220, inferring, based on thedetermining, a chroma intra mode.

The method 1200 includes, at step 1230, performing, based on the chromaintra mode, a conversion between the current video block and a bitstreamrepresentation of the current video block.

In some embodiments, the luma component covers a predetermined chromasample of the chroma component. In an example, the predetermined chromasample is a top-left sample or a center sample of the chroma component.

In some embodiments, the inferred chroma intra mode is a DM mode.

In some embodiments, the inferred chroma intra mode is the ALWIP mode.

In some embodiments, the ALWIP mode is applied to one or more chromacomponents of the current video block.

In some embodiments, different matrix or bias vectors of the ALWIP modeare applied to different color components of the current video block. Inan example, the different matrix or bias vectors are predefined jointlyfor Cb and Cr components. In another example, the Cb and Cr componentsare concatenated. In yet another example, the Cb and Cr components areinterleaved.

FIG. 13 shows a flowchart of an exemplary method for video processing.The method 1300 includes, at step 1310, determining that a current videoblock is coded using an affine linear weighted intra prediction (ALWIP)mode.

The method 1300 includes, at step 1320, performing, based on thedetermining, a conversion between the current video block and abitstream representation of the current video block.

In some embodiments, the determining is based on signaling in a sequenceparameter set (SPS), a picture parameter set (PPS), a slice header, atile group header, a tile header, a coding tree unit (CTU) row or a CTUregion.

In some embodiments, the determining is based on a height (H) or a width(W) of the current video block. In an example, W > T1 or H > T2. Inanother example, W ≥ T1 or H ≥ T2. In yet another example, W < T1 or H <T2. In yet another example, W ≤ T1 or H ≤ T2. In yet another example, T1= 32 and T2 = 32.

In some embodiments, the determining is based on a height (H) or a width(W) of the current video block. In an example, W + H ≤ T. In anotherexample, W + H ≥ T. In yet another example, W × H ≤ T. In yet anotherexample, W × H ≥ T. In yet another example, T = 256.

FIG. 14 shows a flowchart of an exemplary method for video processing.The method 1400 includes, at step 1410, determining that a current videoblock is coded using a coding mode different from an affine linearweighted intra prediction (ALWIP) mode.

The method 1400 includes, at step 1420, performing, based on thedetermining, a conversion between the current video block and abitstream representation of the current video block.

In some embodiments, the coding mode is a combined intra and interprediction (CIIP) mode, and method 1400 further includes the step ofperforming a selection between the ALWIP mode and a normal intraprediction mode. In an example, performing the selection is based on anexplicit signaling in the bitstream representation of the current videoblock. In another example, performing the selection is based onpredetermined rule. In yet another example, the predetermined rulealways selects the ALWIP mode when the current video block is codedusing the CIIP mode. In yet another example, the predetermined rulealways selects the normal intra prediction mode when the current videoblock is coded using the CIIP mode.

In some embodiments, the coding mode is a cross-component linear model(CCLM) prediction mode. In an example, a downsampling procedure for theALWIP mode is based on a downsampling procedure for the CCLM predictionmode. In another example, the downsampling procedure for the ALWIP modeis based on a first set of parameters, and wherein the downsamplingprocedure for the CCLM prediction mode is based on a second set ofparameters different from the first set of parameters. In yet anotherexample, the downsampling procedure for the ALWIP mode or the CCLMprediction mode comprises at least one of a selection of downsampledpositions, a selection of downsampling filters, a rounding operation ora clipping operation.

In some embodiments, the method 1400 further includes the step ofapplying one or more of a Reduced Secondary Transform (RST), a secondarytransform, a rotation transform or a Non-Separable Secondary Transform(NSST).

In some embodiments, the method 1400 further includes the step ofapplying block-based differential pulse coded modulation (DPCM) orresidual DPCM.

In some embodiments, a video processing method includes determining,based on a rule for a current video block, a context of a flagindicative of use of affine linear weighted intra prediction (ALWIP)mode during a conversion between the current video block and a bitstreamrepresentation of the current video block, predicting, based on theALWIP mode, a plurality of sub-blocks of the current video block andperforming, based on the predicting, the conversion between the currentvideo block and a bitstream representation of the current video block.The rule may be specified implicitly using an a priori technique or maybe signaled in the coded bitstream. Other examples and aspects of thismethod are further described in items 37 and 38 in Section 4.

In some embodiments, a method for video processing includes determiningthat a current video block is coded using an affine linear weightedintra prediction (ALWIP) mode, and performing, during a conversionbetween the current video block and a bitstream representation of thecurrent video block, at least two filtering stages on samples of thecurrent video block in an upsampling process associated with the ALWIPmode, wherein a first precision of the samples in a first filteringstage of the at least two filtering stages is different from a secondprecision of the samples in a second filtering stage of the at least twofiltering stages.

In an example, the samples of the current video block are predictionsamples, intermedium samples before the upsampling process orintermedium samples after the upsampling process. In another example,the samples are upsampled in a first dimension horizontally in the firstfiltering stage, and wherein the samples are upsampled in a seconddimension vertically in the second filtering stage. In yet anotherexample, the samples are upsampled in a first dimension vertically inthe first filtering stage, and wherein the samples are upsampled in asecond dimension horizontally in the second filtering stage.

In an example, an output of the first filtering stage is right-shiftedor divided to generate a processed output, and wherein the processedoutput is an input to the second filtering stage. In another example, anoutput of the first filtering stage is left-shifted or multiplied togenerate a processed output, and wherein the processed output is aninput to the second filtering stage. Other examples and aspects of thismethod are further described in item 40 in Section 4.

6 Example Implementations of the Disclosed Technology

FIG. 15 is a block diagram of a video processing apparatus 1500. Theapparatus 1500 may be used to implement one or more of the methodsdescribed herein. The apparatus 1500 may be embodied in a smartphone,tablet, computer, Internet of Things (IoT) receiver, and so on. Theapparatus 1500 may include one or more processors 1502, one or morememories 1504 and video processing hardware 1506. The processor(s) 1502may be configured to implement one or more methods (including, but notlimited to, methods 1100-1400 and 2100-2400) described in the presentdocument. The memory (memories) 1504 may be used for storing data andcode used for implementing the methods and techniques described herein.The video processing hardware 1506 may be used to implement, in hardwarecircuitry, some techniques described in the present document.

In some embodiments, the video coding methods may be implemented usingan apparatus that is implemented on a hardware platform as describedwith respect to FIG. 15 .

Some embodiments of the disclosed technology include making a decisionor determination to enable a video processing tool or mode. In anexample, when the video processing tool or mode is enabled, the encoderwill use or implement the tool or mode in the processing of a block ofvideo, but may not necessarily modify the resulting bitstream based onthe usage of the tool or mode. That is, a conversion from the block ofvideo to the bitstream representation of the video will use the videoprocessing tool or mode when it is enabled based on the decision ordetermination. In another example, when the video processing tool ormode is enabled, the decoder will process the bitstream with theknowledge that the bitstream has been modified based on the videoprocessing tool or mode. That is, a conversion from the bitstreamrepresentation of the video to the block of video will be performedusing the video processing tool or mode that was enabled based on thedecision or determination.

Some embodiments of the disclosed technology include making a decisionor determination to disable a video processing tool or mode. In anexample, when the video processing tool or mode is disabled, the encoderwill not use the tool or mode in the conversion of the block of video tothe bitstream representation of the video. In another example, when thevideo processing tool or mode is disabled, the decoder will process thebitstream with the knowledge that the bitstream has not been modifiedusing the video processing tool or mode that was disabled based on thedecision or determination.

FIG. 17 is a block diagram that illustrates an example video codingsystem 100 that may utilize the techniques of this disclosure. As shownin FIG. 17 , video coding system 100 may include a source device 110 anda destination device 120. Source device 110 generates encoded video datawhich may be referred to as a video encoding device. Destination device120 may decode the encoded video data generated by source device 110which may be referred to as a video decoding device. Source device 110may include a video source 112, a video encoder 114, and an input/output(I/O) interface 116.

Video source 112 may include a source such as a video capture device, aninterface to receive video data from a video content provider, and/or acomputer graphics system for generating video data, or a combination ofsuch sources. The video data may comprise one or more pictures. Videoencoder 114 encodes the video data from video source 112 to generate abitstream. The bitstream may include a sequence of bits that form acoded representation of the video data. The bitstream may include codedpictures and associated data. The coded picture is a codedrepresentation of a picture. The associated data may include sequenceparameter sets, picture parameter sets, and other syntax structures. I/Ointerface 116 may include a modulator/demodulator (modem) and/or atransmitter. The encoded video data may be transmitted directly todestination device 120 via I/O interface 116 through network 130 a. Theencoded video data may also be stored onto a storage medium/server 130 bfor access by destination device 120.

Destination device 120 may include an I/O interface 126, a video decoder124, and a display device 122.

I/O interface 126 may include a receiver and/or a modem. I/O interface126 may acquire encoded video data from the source device 110 or thestorage medium/ server 130 b. Video decoder 124 may decode the encodedvideo data. Display device 122 may display the decoded video data to auser. Display device 122 may be integrated with the destination device120, or may be external to destination device 120 which be configured tointerface with an external display device.

Video encoder 114 and video decoder 124 may operate according to a videocompression standard, such as the High Efficiency Video Coding (HEVC)standard, Versatile Video Coding(VVM) standard and other current and/orfurther standards.

FIG. 18 is a block diagram illustrating an example of video encoder 200,which may be video encoder 114 in the system 100 illustrated in FIG. 17.

Video encoder 200 may be configured to perform any or all of thetechniques of this disclosure. In the example of FIG. 18 , video encoder200 includes a plurality of functional components. The techniquesdescribed in this disclosure may be shared among the various componentsof video encoder 200. In some examples, a processor may be configured toperform any or all of the techniques described in this disclosure.

The functional components of video encoder 200 may include a partitionunit 201, a prediction unit 202 which may include a mode select unit203, a motion estimation unit 204, a motion compensation unit 205 and anintra prediction unit 206, a residual generation unit 207, a transformunit 208, a quantization unit 209, an inverse quantization unit 210, aninverse transform unit 211, a reconstruction unit 212, a buffer 213, andan entropy encoding unit 214.

In other examples, video encoder 200 may include more, fewer, ordifferent functional components. In an example, prediction unit 202 mayinclude an intra block copy (IBC) unit. The IBC unit may performprediction in an IBC mode in which at least one reference picture is apicture where the current video block is located.

Furthermore, some components, such as motion estimation unit 204 andmotion compensation unit 205 may be highly integrated, but arerepresented in the example of FIG. 18 separately for purposes ofexplanation.

Partition unit 201 may partition a picture into one or more videoblocks. Video encoder 200 and video decoder 300 may support variousvideo block sizes.

Mode select unit 203 may select one of the coding modes, intra or inter,e.g., based on error results, and provide the resulting intra- orinter-coded block to a residual generation unit 207 to generate residualblock data and to a reconstruction unit 212 to reconstruct the encodedblock for use as a reference picture. In some example, Mode select unit203 may select a combination of intra and inter prediction (CIIP) modein which the prediction is based on an inter prediction signal and anintra prediction signal. Mode select unit 203 may also select aresolution for a motion vector (e.g., a sub-pixel or integer pixelprecision) for the block in the case of inter-prediction.

To perform inter prediction on a current video block, motion estimationunit 204 may generate motion information for the current video block bycomparing one or more reference frames from buffer 213 to the currentvideo block. Motion compensation unit 205 may determine a predictedvideo block for the current video block based on the motion informationand decoded samples of pictures from buffer 213 other than the pictureassociated with the current video block.

Motion estimation unit 204 and motion compensation unit 205 may performdifferent operations for a current video block, for example, dependingon whether the current video block is in an I slice, a P slice, or a Bslice.

In some examples, motion estimation unit 204 may perform uni-directionalprediction for the current video block, and motion estimation unit 204may search reference pictures of list 0 or list 1 for a reference videoblock for the current video block. Motion estimation unit 204 may thengenerate a reference index that indicates the reference picture in list0 or list 1 that contains the reference video block and a motion vectorthat indicates a spatial displacement between the current video blockand the reference video block. Motion estimation unit 204 may output thereference index, a prediction direction indicator, and the motion vectoras the motion information of the current video block. Motioncompensation unit 205 may generate the predicted video block of thecurrent block based on the reference video block indicated by the motioninformation of the current video block.

In other examples, motion estimation unit 204 may perform bi-directionalprediction for the current video block, motion estimation unit 204 maysearch the reference pictures in list 0 for a reference video block forthe current video block and may also search the reference pictures inlist 1 for another reference video block for the current video block.Motion estimation unit 204 may then generate reference indexes thatindicate the reference pictures in list 0 and list 1 containing thereference video blocks and motion vectors that indicate spatialdisplacements between the reference video blocks and the current videoblock. Motion estimation unit 204 may output the reference indexes andthe motion vectors of the current video block as the motion informationof the current video block. Motion compensation unit 205 may generatethe predicted video block of the current video block based on thereference video blocks indicated by the motion information of thecurrent video block.

In some examples, motion estimation unit 204 may output a full set ofmotion information for decoding processing of a decoder.

In some examples, motion estimation unit 204 may not output a full setof motion information for the current video. Rather, motion estimationunit 204 may signal the motion information of the current video blockwith reference to the motion information of another video block. Forexample, motion estimation unit 204 may determine that the motioninformation of the current video block is sufficiently similar to themotion information of a neighboring video block.

In one example, motion estimation unit 204 may indicate, in a syntaxstructure associated with the current video block, a value thatindicates to the video decoder 300 that the current video block has thesame motion information as another video block.

In another example, motion estimation unit 204 may identify, in a syntaxstructure associated with the current video block, another video blockand a motion vector difference (MVD). The motion vector differenceindicates a difference between the motion vector of the current videoblock and the motion vector of the indicated video block. The videodecoder 300 may use the motion vector of the indicated video block andthe motion vector difference to determine the motion vector of thecurrent video block.

As discussed above, video encoder 200 may predictively signal the motionvector. Two examples of predictive signaling techniques that may beimplemented by video encoder 200 include advanced motion vectorprediction (AMVP) and merge mode signaling.

Intra prediction unit 206 may perform intra prediction on the currentvideo block. When intra prediction unit 206 performs intra prediction onthe current video block, intra prediction unit 206 may generateprediction data for the current video block based on decoded samples ofother video blocks in the same picture. The prediction data for thecurrent video block may include a predicted video block and varioussyntax elements.

Residual generation unit 207 may generate residual data for the currentvideo block by subtracting (e.g., indicated by the minus sign) thepredicted video block(s) of the current video block from the currentvideo block. The residual data of the current video block may includeresidual video blocks that correspond to different sample components ofthe samples in the current video block.

In other examples, there may be no residual data for the current videoblock for the current video block, for example in a skip mode, andresidual generation unit 207 may not perform the subtracting operation.

Transform processing unit 208 may generate one or more transformcoefficient video blocks for the current video block by applying one ormore transforms to a residual video block associated with the currentvideo block.

After transform processing unit 208 generates a transform coefficientvideo block associated with the current video block, quantization unit209 may quantize the transform coefficient video block associated withthe current video block based on one or more quantization parameter (QP)values associated with the current video block.

Inverse quantization unit 210 and inverse transform unit 211 may applyinverse quantization and inverse transforms to the transform coefficientvideo block, respectively, to reconstruct a residual video block fromthe transform coefficient video block. Reconstruction unit 212 may addthe reconstructed residual video block to corresponding samples from oneor more predicted video blocks generated by the prediction unit 202 toproduce a reconstructed video block associated with the current blockfor storage in the buffer 213.

After reconstruction unit 212 reconstructs the video block, loopfiltering operation may be performed reduce video blocking artifacts inthe video block.

Entropy encoding unit 214 may receive data from other functionalcomponents of the video encoder 200. When entropy encoding unit 214receives the data, entropy encoding unit 214 may perform one or moreentropy encoding operations to generate entropy encoded data and outputa bitstream that includes the entropy encoded data.

FIG. 19 is a block diagram illustrating an example of video decoder 300which may be video decoder 124 in the system 100 illustrated in FIG. 17.

The video decoder 300 may be configured to perform any or all of thetechniques of this disclosure. In the example of FIG. 19 , the videodecoder 300 includes a plurality of functional components. Thetechniques described in this disclosure may be shared among the variouscomponents of the video decoder 300. In some examples, a processor maybe configured to perform any or all of the techniques described in thisdisclosure.

In the example of FIG. 19 , video decoder 300 includes an entropydecoding unit 301, a motion compensation unit 302, an intra predictionunit 303, an inverse quantization unit 304,an inverse transformationunit 305 , and a reconstruction unit 306 and a buffer 307. Video decoder300 may, in some examples, perform a decoding pass generally reciprocalto the encoding pass described with respect to video encoder 200 (FIG.18 ).

Entropy decoding unit 301 may retrieve an encoded bitstream. The encodedbitstream may include entropy coded video data (e.g., encoded blocks ofvideo data). Entropy decoding unit 301 may decode the entropy codedvideo data, and from the entropy decoded video data, motion compensationunit 302 may determine motion information including motion vectors,motion vector precision, reference picture list indexes, and othermotion information. Motion compensation unit 302 may, for example,determine such information by performing the AMVP and merge mode.

Motion compensation unit 302 may produce motion compensated blocks,possibly performing interpolation based on interpolation filters.Identifiers for interpolation filters to be used with sub-pixelprecision may be included in the syntax elements.

Motion compensation unit 302 may use interpolation filters as used byvideo encoder 20 during encoding of the video block to calculateinterpolated values for sub-integer pixels of a reference block. Motioncompensation unit 302 may determine the interpolation filters used byvideo encoder 200 according to received syntax information and use theinterpolation filters to produce predictive blocks.

Motion compensation unit 302 may use some of the syntax information todetermine sizes of blocks used to encode frame(s) and/or slice(s) of theencoded video sequence, partition information that describes how eachmacroblock of a picture of the encoded video sequence is partitioned,modes indicating how each partition is encoded, one or more referenceframes (and reference frame lists) for each inter-encoded block, andother information to decode the encoded video sequence.

Intra prediction unit 303 may use intra prediction modes for examplereceived in the bitstream to form a prediction block from spatiallyadjacent blocks. Inverse quantization unit 303 inverse quantizes, i.e.,de-quantizes, the quantized video block coefficients provided in thebitstream and decoded by entropy decoding unit 301. Inverse transformunit 303 applies an inverse transform.

Reconstruction unit 306 may sum the residual blocks with thecorresponding prediction blocks generated by motion compensation unit302 or intra-prediction unit 303 to form decoded blocks. If desired, adeblocking filter may also be applied to filter the decoded blocks inorder to remove blockiness artifacts. The decoded video blocks are thenstored in buffer 307, which provides reference blocks for subsequentmotion compensation/intra prediction and also produces decoded video forpresentation on a display device.

FIG. 20 is a block diagram showing an example video processing system2000 in which various techniques disclosed herein may be implemented.Various implementations may include some or all of the components of thesystem 2000. The system 2000 may include input 2002 for receiving videocontent. The video content may be received in a raw or uncompressedformat, e.g., 8 or 10 bit multi-component pixel values, or may be in acompressed or encoded format. The input 2002 may represent a networkinterface, a peripheral bus interface, or a storage interface. Examplesof network interface include wired interfaces such as Ethernet, passiveoptical network (PON), etc. and wireless interfaces such as wirelessfidelity (Wi-Fi) or cellular interfaces.

The system 2000 may include a coding component 2004 that may implementthe various coding or encoding methods described in the presentdocument. The coding component 2004 may reduce the average bitrate ofvideo from the input 2002 to the output of the coding component 2004 toproduce a coded representation of the video. The coding techniques aretherefore sometimes called video compression or video transcodingtechniques. The output of the coding component 2004 may be eitherstored, or transmitted via a communication connected, as represented bythe component 2006. The stored or communicated bitstream (or coded)representation of the video received at the input 2002 may be used bythe component 2008 for generating pixel values or displayable video thatis sent to a display interface 2010. The process of generatinguser-viewable video from the bitstream representation is sometimescalled video decompression. Furthermore, while certain video processingoperations are referred to as “coding” operations or tools, it will beappreciated that the coding tools or operations are used at an encoderand corresponding decoding tools or operations that reverse the resultsof the coding will be performed by a decoder.

Examples of a peripheral bus interface or a display interface mayinclude universal serial bus (USB) or high definition multimediainterface (HDMI) or Displayport, and so on. Examples of storageinterfaces include serial advanced technology attachment (SATA),peripheral component interconnect (PCI), integrated drive electronics(IDE) interface, and the like. The techniques described in the presentdocument may be embodied in various electronic devices such as mobilephones, laptops, smartphones or other devices that are capable ofperforming digital data processing and/or video display.

In some embodiments, the ALWIP mode or the MIP mode is used to compute aprediction block of the current video block by performing, on previouslycoded samples of the video, a boundary downsampling operation (or anaveraging operation), followed by a matrix vector multiplicationoperation, and selectively (or optionally) followed by an upsamplingoperation (or a linear interpolation operation). In some embodiments,the ALWIP mode or the MIP mode is used to compute a prediction block ofthe current video block by performing, on previously coded samples ofthe video, a boundary downsampling operation (or an averaging operation)and followed by a matrix vector multiplication operation. In someembodiments, the ALWIP mode or the MIP mode can also perform anupsampling operation (or a linear interpolation operation) afterperforming the matrix vector multiplication operation.

FIG. 21 describes an example method 2100 for a matrix-based intraprediction. Operation 2102 includes performing a conversion between acurrent video block of a video and a bitstream representation of thecurrent video block using a matrix based intra prediction (MIP) mode inwhich a prediction block of the current video block is determined byperforming, on reference boundary samples located to a left of thecurrent video block and located to a top of the current video block, aboundary downsampling operation, followed by a matrix vectormultiplication operation, and selectively followed by an upsamplingoperation, where instead of reduced boundary samples calculated from thereference boundary samples of the current video block in the boundarydownsampling operation, the reference boundary samples are directly usedfor a prediction process in the upsampling operation.

In some embodiments for method 2100, the reference boundary sampleslocated at positions associated with the upsampling boundary samples ofthe current video block are directly used for the prediction process inthe upsampling operation. In some embodiments for method 2100,upsampling boundary samples are not computed by averaging multipleadjacent reference boundary samples. In some embodiments for method2100, the reduced boundary samples are calculated from the referenceboundary samples of the current video block and a downscaling factor. Insome embodiments for method 2100, the boundary downsampling operationincludes a one-stage boundary sample downsampling operation. In someembodiments for method 2100, the downscaling factor is calculated by atransform block size and a downsampled boundary size.

FIG. 22 describes an example method 2200 for a matrix-based intraprediction. Operation 2202 includes performing, during a conversionbetween a current video block of a video and a bitstream representationof the current video block, at least two filtering stages on samples ofthe current video block in an upsampling operation associated with amatrix based intra prediction (MIP) mode in which a prediction block ofthe current video block is determined by performing, on previously codedsamples of the video, a boundary downsampling operation, followed by amatrix vector multiplication operation, and selectively followed by theupsampling operation, where a first precision of the samples in a firstfiltering stage of the at least two filtering stages is different from asecond precision of the samples in a second filtering stage of the atleast two filtering stages. Operation 2204 includes performing theconversion between the current video block and the bitstreamrepresentation of the current video block.

In some embodiments for method 2200, the samples of the current videoblock are prediction samples, intermediate samples before the upsamplingoperation, or intermediate samples after the upsampling operation. Insome embodiments for method 2200, the samples are upsampled in a firstdimension horizontally in the first filtering stage, the samples areupsampled in a second dimension vertically in the second filteringstage, and the first filtering stage precedes the second filteringstage. In some embodiments for method 2200, the samples are upsampled ina first dimension vertically in the first filtering stage, the samplesare upsampled in a second dimension horizontally in the second filteringstage, and the first filtering stage precedes the second filteringstage.

In some embodiments for method 2200, output upsampling results of thefirst filtering stage provides input samples to the second filteringstage, and the first filtering stage excludes performing aright-shifting operation or a dividing operation on the samples. In someembodiments for method 2200, a final up-sampled result is obtained byright-shifting by a variable Shift1 or dividing by a variable Dem1 theinput samples of the second filtering stage. In some embodiments formethod 2200, a final up-sampled result is obtained by right-shifting bya variable Shift2 or by dividing by a variable Dem2 output upsamplingresults of the first filtering stage. In some embodiments for method2200, the variable Shift1 = 2 × the variable Shift2, and wherein thevariable Dem1 = the variable Dem2 × the variable Dem2. In someembodiments for method 2200, at least some of the samples of the currentvideo block are left shifted by a variable Shift3 or multiplied by avariable Dem3 before being sent to the second filtering stage, and theat least some of the samples are not output upsampling results of thefirst filtering stage. In some embodiments for method 2200, the variableShift3 = the variable Shift1, and wherein the variable Dem3 = thevariable Dem2.

In some embodiments for method 2200, output upsampling results of thefirst filtering stage is right-shifted by a variable Shift1 or dividedby a variable Dem1 to generate a processed output, and the processedoutput provides input samples to the second filtering stage. In someembodiments for method 2200, a final up-sampled result is obtained byright-shifting by a variable Shift2 or dividing by a variable Dem2 theinput samples of the second filtering stage. In some embodiments formethod 2200, the variable Shift2 is not equal to the variable Shift1 andthe variable Dem2 is not equal to the variable Dem1. In some embodimentsfor method 2200, the variable Shift2 is greater than the variable Shift1and the variable Dem2 is greater than the variable Dem1. In someembodiments for method 2200, a final up-sampled result is obtained byright-shifting by a variable Shift3 or dividing by a variable Dem3 theoutput upsampling filtering results of the first filtering stage. Insome embodiments for method 2200, the variable Shift3 is equal to thevariable Shift1, and wherein the variable Dem3 is not equal to thevariable Dem1.

In some embodiments for method 2200, the variable Shift3 = the variableShift1 + the variable Shift2. In some embodiments for method 2200, atleast some of the samples of the current video block are left shifted ormultiplied before being sent to the second filtering stage, and the atleast some of the samples are not the output upsampling results of thefirst filtering stage. In some embodiments for method 2200, outputupsampling results of the first filtering stage is left-shifted by avariable Shift1 or multiplied or a variable Dem1 to generate a processedoutput, and the processed output provides input samples to the secondfiltering stage. In some embodiments for method 2200, a final up-sampledresult is obtained by right-shifting by a factor or by dividing by thefactor the input samples of the second filtering stage.

In some embodiments for method 2200, a final up-sampled result isobtained by right-shifting by a factor or by dividing by the factor theoutput upsampling filtering results of the first filtering stage. Insome embodiments for method 2200, at least some of the samples of thecurrent video block are left shifted by a variable Shift2 or multipliedby a variable Dem2 before being sent to the second filtering stage, andthe at least some of the samples are not the output upsampling resultsof the first filtering stage. In some embodiments for method 2200, thevariable Shift 2 is not equal to the variable Shift1, and wherein thevariable Dem2 is not equal to the variable Dem1. In some embodiments formethod 2200, the variable Shift2 is greater than the variable Shift1 andthe variable Dem2 is greater than the variable Dem1.

In some embodiments for method 2200, the samples that are input to thefirst filtering stage are left-shifted by a variable Shift1 ormultiplied by a variable Dem1 to generate a processed output, and theprocessed output provides input samples to the second filtering stage.In some embodiments for method 2200, a final up-sampled result isobtained by right-shifting by a factor or by dividing by the factor theinput samples of the second filtering stage. In some embodiments formethod 2200, a final up-sampled result is obtained by right-shifting bya factor or by dividing by the factor the processed output of the firstfiltering stage. In some embodiments for method 2200, at least some ofthe samples of the current video block are left shifted by a variableShift2 or multiplied by a variable Dem2 before being sent to the secondfiltering stage, and the at least some of the samples are not outputupsampling results of the first filtering stage. In some embodiments formethod 2200, the variable Shift2 is not equal to the variable Shift1,and wherein the variable Dem2 is not equal to the variable Dem 1. Insome embodiments for method 2200, the variable Shift2 is greater thanthe variable Shift1 and the variable Dem2 is greater than the variableDem1.

FIG. 23 describes an example video encoding method 2300 for amatrix-based intra prediction. Operation 2302 includes encoding acurrent video block of a video using a matrix intra prediction (MIP)mode in which a prediction block of the current video block isdetermined by performing, on previously coded samples of the video, aboundary downsampling operation, followed by a matrix vectormultiplication operation, and selectively followed by an upsamplingoperation. Operation 2304 includes adding, to a coded representation ofthe current video block, a syntax element indicative of applicability ofthe MIP mode to the current video block using arithmetic coding in whicha context for the syntax element is derived based on a rule.

FIG. 24 describes an example video decoding method 2400 for amatrix-based intra prediction. Operation 2402 parsing a codedrepresentation of a video comprising a current video block for a syntaxelement indicating whether the current video block is coded using amatrix intra prediction (MIP) mode, wherein the syntax element is codedusing arithmetic coding in which a context for the syntax element isderived based on a rule. Operation 2404 includes decoding the codedrepresentation of the current video block to generate a decoded currentvideo block, wherein in a case that the current video block is codedusing the MIP mode, the decoding includes determining a prediction blockof the current video block by performing, on previously coded samples ofthe video, a boundary downsampling operation, followed by a matrixvector multiplication operation, and selectively followed by anupsampling operation.

In some embodiments for method(s) 2300 and/or 2400, the rule definesthat the context for the syntax element is derived in response to(Abs(Log2(cbWidth) - Log2(cbHeight)) being greater than 1, whereincbWidth is a width of the current video block, and wherein cbHeight is aheight of the current video block. In some embodiments for method(s)2300 and/or 2400, the rule defines that the context of the syntaxelement is derived in response to (Abs(Log2(cbWidth) - Log2(cbHeight))being less than 1, wherein cbWidth is a width of the current videoblock, and wherein cbHeight is a height of the current video block. Insome embodiments for method(s) 2300 and/or 2400, the rule specifies thatthe context for the syntax element is derived by using the MIP moderelated information of one or more neighboring video blocks of thecurrent video block and/or availability of the one or more neighboringvideo blocks.

In some embodiments for method(s) 2300 and/or 2400, the context for thesyntax element is derived based on: a first MIP syntax element of a leftneighboring video block of the current video block, a second MIP syntaxelement of a top neighboring video block of the current video block, andan availability of the left neighboring video block and the topneighboring video block. In some embodiments for method(s) 2300 and/or2400, the context (offset ctxInc) is derived based on a followingequation: offset ctxInc = (condL && availableL) + (condA &&availableA) + ctxSetIdx * 3, wherein condL is a first MIP syntax elementof a left neighboring video block of the current video block, whereincondA is a second MIP syntax element of a top neighboring video block ofthe current video block, wherein availableL and availableA indicate anavailability of the left neighboring video block and the top neighboringvideo block, respectively, wherein && indicates a logical And operation,and wherein ctxSetIdx is a predefined context index.

In some embodiments for method(s) 2300 and/or 2400, context is derivedbased on: a MIP syntax element of a left neighboring video block of thecurrent video block, and an availability of the left neighboring videoblock. In some embodiments for method(s) 2300 and/or 2400, the context(offset ctxInc) is derived based on a following equation: offset ctxInc= (condL && availableL ) + ctxSetIdx * 3, wherein condL is the MIPsyntax element of the left neighboring video block of the current videoblock, wherein availableL indicate an availability of the leftneighboring video block, wherein && indicates a logical And operation,and wherein ctxSetIdx is a predefined context index.

In some embodiments for method(s) 2300 and/or 2400, context is derivedbased on: a MIP syntax element of a top neighboring video block of thecurrent video block, and an availability of the top neighboring videoblock. In some embodiments for method(s) 2300 and/or 2400, the context(offset ctxInc) is derived based on a following equation: offset ctxInc= (condA && availableA) + ctxSetIdx * 3, wherein condA is the MIP syntaxelement of the top neighboring video block of the current video block,wherein availableA indicate an availability of the top neighboring videoblock, wherein && indicates a logical And operation, and whereinctxSetIdx is a predefined context index. In some embodiments formethod(s) 2300 and/or 2400, the predefined context index ctxSetIdx isequal to zero. In some embodiments for method(s) 2300 and/or 2400, therule specifies that the context for the syntax element is one fixedcontext with which the syntax element is coded using the arithmeticcoding. In some embodiments for method(s) 2300 and/or 2400, the rulespecifies that the syntax element is bypass coded using the arithmeticcoding.

In some embodiments for method(s) 2300 and/or 2400, the rule specifiesthat the context is derived from K contexts, where K is greater than orequal to 2. In some embodiments for method(s) 2300 and/or 2400, a firstcontext in an order from the K contexts is used in response to W > N * Hor H > N * W, and wherein N is 2. In some embodiments for method(s) 2300and/or 2400, a second context in an order from the K contexts is used inresponse to W ≤ N * H or H ≤ N * W, and wherein N is 2. In someembodiments for method(s) 2300 and/or 2400, the rule specifies that thecontext is derived from N other contexts, where N is greater than orequal to zero. In some embodiments for method(s) 2300 and/or 2400, N isequal to 3, the context for the syntax element is derived by using twoMIP syntax elements of two video blocks and/or availability of the twovideo blocks, and the two video blocks are two neighboring video blocksof the current video block or the two video blocks are two non-adjacentvideo blocks of the current video block.

In some embodiments for method(s) 2300 and/or 2400, the two neighboringvideo blocks include a top neighboring video block relative to thecurrent video block and a left neighboring video block relative to thecurrent video block. In some embodiments for method(s) 2300 and/or 2400,the top neighboring video block covers a position (x0, y0 - 1) and theleft neighboring video block covers a position (x0 - 1, y0), wherein aluma location (x0, y0) specifies a top-left sample of the current videoblock. In some embodiments for method(s) 2300 and/or 2400, the twoneighboring video blocks include a top neighboring video block relativeto the current video block and a below-left neighboring video blockrelative to the current video block. In some embodiments for method(s)2300 and/or 2400, the two neighboring video blocks include a topneighboring video block relative to the current video block and atop-right neighboring video block relative to the current video block.In some embodiments for method(s) 2300 and/or 2400, the two neighboringvideo blocks include a top-right neighboring video block relative to thecurrent video block and a left neighboring video block relative to thecurrent video block.

In some embodiments for method(s) 2300 and/or 2400, the two neighboringvideo blocks include a top-right neighboring video block relative to thecurrent video block and a below-left neighboring video block relative tothe current video block. In some embodiments for method(s) 2300 and/or2400, the two neighboring video blocks include a left neighboring videoblock relative to the current video block and a below-left neighboringvideo block relative to the current video block. In some embodiments formethod(s) 2300 and/or 2400, the two neighboring video blocks include anytwo of: a top-right neighboring video block relative to the currentvideo block, a top neighboring video block relative to the current videoblock, a top-left neighboring video block relative to the current videoblock, a left neighboring video block relative to the current videoblock, and a below-left neighboring video block relative to the currentvideo block.

In some embodiments for method(s) 2300 and/or 2400, N is equal to 2, thecontext for the syntax element is derived by using one MIP syntaxelement of one video block and/or availability of the one video block,and the one video block is a neighboring video block of the currentvideo block or the one video block is a non-adjacent video block of thecurrent video block. In some embodiments for method(s) 2300 and/or 2400,the one neighboring video block include any one of: a top-rightneighboring video block relative to the current video block, a topneighboring video block relative to the current video block, a top-leftneighboring video block relative to the current video block, a leftneighboring video block relative to the current video block, and abelow-left neighboring video block relative to the current video block.In some embodiments for method(s) 2300 and/or 2400, the rule specifiesthat the context for the syntax element is one fixed context with whichthe syntax element is coded using the arithmetic coding. In someembodiments for method(s) 2300 and/or 2400, the rule specifies that thesyntax element is bypass coded using the arithmetic coding.

From the foregoing, it will be appreciated that specific embodiments ofthe presently disclosed technology have been described herein forpurposes of illustration, but that various modifications may be madewithout deviating from the scope of the present disclosure. Accordingly,the presently disclosed technology is not limited except as by theappended claims.

Implementations of the subject matter and the functional operationsdescribed in this patent document can be implemented in various systems,digital electronic circuitry, or in computer software, firmware, orhardware, including the structures disclosed in this specification andtheir structural equivalents, or in combinations of one or more of them.Implementations of the subject matter described in this specificationcan be implemented as one or more computer program products, i.e., oneor more modules of computer program instructions encoded on a tangibleand non-transitory computer readable medium for execution by, or tocontrol the operation of, data processing apparatus. The computerreadable medium can be a machine-readable storage device, amachine-readable storage substrate, a memory device, a composition ofmatter effecting a machine-readable propagated signal, or a combinationof one or more of them. The term “data processing unit” or “dataprocessing apparatus” encompasses all apparatus, devices, and machinesfor processing data, including by way of example a programmableprocessor, a computer, or multiple processors or computers. Theapparatus can include, in addition to hardware, code that creates anexecution environment for the computer program in question, e.g., codethat constitutes processor firmware, a protocol stack, a databasemanagement system, an operating system, or a combination of one or moreof them.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, and it can bedeployed in any form, including as a stand-alone program or as a module,component, subroutine, or other unit suitable for use in a computingenvironment. A computer program does not necessarily correspond to afile in a file system. A program can be stored in a portion of a filethat holds other programs or data (e.g., one or more scripts stored in amarkup language document), in a single file dedicated to the program inquestion, or in multiple coordinated files (e.g., files that store oneor more modules, sub programs, or portions of code). A computer programcan be deployed to be executed on one computer or on multiple computersthat are located at one site or distributed across multiple sites andinterconnected by a communication network.

The processes and logic flows described in this specification can beperformed by one or more programmable processors executing one or morecomputer programs to perform functions by operating on input data andgenerating output. The processes and logic flows can also be performedby, and apparatus can also be implemented as, special purpose logiccircuitry, e.g., a field programmable gate array (FPGA) or anapplication specific integrated circuit (ASIC).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read only memory ora random access memory or both. The essential elements of a computer area processor for performing instructions and one or more memory devicesfor storing instructions and data. Generally, a computer will alsoinclude, or be operatively coupled to receive data from or transfer datato, or both, one or more mass storage devices for storing data, e.g.,magnetic, magneto optical disks, or optical disks. However, a computerneed not have such devices. Computer readable media suitable for storingcomputer program instructions and data include all forms of nonvolatilememory, media and memory devices, including by way of examplesemiconductor memory devices, e.g., erasable programmable read-onlymemory (EPROM), electrically erasable programmable read-only memory(EEPROM), and flash memory devices; magnetic disks, e.g., internal harddisks or removable disks; magneto optical disks; and compact disc,read-only memory (CD ROM) and digital versatile disc read-only memory(DVD-ROM) disks. The processor and the memory can be supplemented by, orincorporated in, special purpose logic circuitry.

It is intended that the specification, together with the drawings, beconsidered exemplary only, where exemplary means an example. As usedherein, the use of “or” is intended to include “and/or”, unless thecontext clearly indicates otherwise.

While this patent document contains many specifics, these should not beconstrued as limitations on the scope of any embodiment or of what maybe claimed, but rather as descriptions of features that may be specificto particular embodiments of particular embodiments. Certain featuresthat are described in this patent document in the context of separateembodiments can also be implemented in combination in a singleembodiment. Conversely, various features that are described in thecontext of a single embodiment can also be implemented in multipleembodiments separately or in any suitable subcombination. Moreover,although features may be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from thecombination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. Moreover, the separation of various system components in theembodiments described in this patent document should not be understoodas requiring such separation in all embodiments.

Only a few implementations and examples are described and otherimplementations, enhancements and variations can be made based on whatis described and illustrated in this patent document.

What is claimed is:
 1. A method of processing video data, comprising:determining, for a conversion between a current video block of a videoand a bitstream of the video, whether a matrix intra prediction (MIP)mode is applied on the current video block based on a syntax element,wherein in the MIP mode, prediction samples of the current video blockare determined by performing a matrix vector multiplication operation;and performing the conversion based on the determining, wherein at leastone bin of the syntax element is context coded, and an increasementvalue of the context is determined based on characteristics of aneighboring block of the current video block, and wherein a boundarydown-sampling operation on reference samples of the current video blockand an up-sampling operation are included in the MIP mode based on asize of the current video block.
 2. The method of claim 1, wherein theincreasement value of the context is determined further based on thesize of the current video block.
 3. The method of claim 2, wherein inresponse to a width-height ratio of the current video block beinggreater than 2, a context with a first predefined increasement value isused for coding the at least one bin of the syntax element.
 4. Themethod of claims 3, wherein in response to a width-height ratio of thecurrent video block being smaller than or equal to 2, a context with asecond increasement value is used for coding the at least one bin of thesyntax element, wherein the second increasement value is not identicalto the first predefined increasement value.
 5. The method of claim 4,wherein the second increasement value is selected from an increasementvalue group based on the characteristics of the neighboring block. 6.The method of claim 5, wherein the characteristics of the neighboringblock include coding mode of the neighboring block and availability ofthe neighboring block.
 7. The method of claim 6, wherein a leftneighboring video block of the current video block and a top neighboringvideo block of the current video block are used to select the secondincreasement value.
 8. The method of claim 7, wherein the secondincreasement value is derived based on a following equation: ctxInc = (condL && availableL ) + ( condA && availableA), wherein condL is a firstMIP syntax element of the left neighboring video block of the currentvideo block, wherein condA is a second MIP syntax element of the topneighboring video block of the current video block, wherein availableLand availableA indicate the availability of the left neighboring videoblock and the top neighboring video block, respectively, and wherein &&indicates a logical And operation.
 9. The method of claim 1, wherein inthe boundary down-sampling operation, reduced boundary samples aredirectly generated from the reference samples and a downscaling factorwithout generating intermediate samples.
 10. The method of claim 9,wherein the downscaling factor is calculated based on a width or heightof the current video block and a boundary size value.
 11. The method ofclaim 1, wherein the MIP mode includes multiple types, and a type indexfor the current video block is derived excluding referring to typeindices of previous video blocks.
 12. The method of claim 11, whereinthe type index for the current video block is explicitly included in thebitstream.
 13. The method of claim 1, wherein the conversion includesencoding the current video block into the bitstream.
 14. The method ofclaim 1, wherein the conversion includes decoding the current videoblock from the bitstream.
 15. An apparatus for processing video datacomprising a processor and a non-transitory memory with instructionsthereon, wherein the instructions upon execution by the processor, causethe processor to: determine, for a conversion between a current videoblock of a video and a bitstream of the video, whether a matrix intraprediction (MIP) mode is applied on the current video block based on asyntax element, wherein in the MIP mode, prediction samples of thecurrent video block are determined by performing a matrix vectormultiplication operation; and perform the conversion based on thedetermining, wherein at least one bin of the syntax element is contextcoded, and an increasement value of the context is determined based oncharacteristics of a neighboring block of the current video block, andwherein a boundary down-sampling operation on reference samples of thecurrent video block and an up-sampling operation are included in the MIPmode based on a size of the current video block.
 16. The apparatus ofclaim 15, wherein the increasement value of the context is determinedfurther based on the size of the current video block, and wherein inresponse to a width-height ratio of the current video block beinggreater than 2, a context with a first predefined increasement value isused for coding the at least one bin of the syntax element, and inresponse to a width-height ratio of the current video block beingsmaller than or equal to 2, a context with a second increasement valueis used for coding the at least one bin of the syntax element, whereinthe second increasement value is not identical to the first predefinedincreasement value.
 17. The apparatus of claim 16, wherein the secondincreasement value is derived based on a following equation: ctx=(condL&& availableL)+(condA && availableA), wherein condL is a first MIPsyntax element of a left neighboring video block of the current videoblock, wherein condA is a second MIP syntax element of a top neighboringvideo block of the current video block, wherein availableL andavailableA indicate the availability of the left neighboring video blockand the top neighboring video block, respectively, and wherein &&indicates a logical And operation.
 18. A non-transitorycomputer-readable storage medium storing instructions that cause aprocessor to: determine, for a conversion between a current video blockof a video and a bitstream of the video, whether a matrix intraprediction (MIP) mode is applied on the current video block based on asyntax element, wherein in the MIP mode, prediction samples of thecurrent video block are determined by performing a matrix vectormultiplication operation; and perform the conversion based on thedetermining, wherein at least one bin of the syntax element is contextcoded, and an increasement value of the context is determined based oncharacteristics of a neighboring block of the current video block, andwherein a boundary down-sampling operation on reference samples of thecurrent video block and an up-sampling operation are included in the MIPmode based on a size of the current video block.
 19. The non-transitorycomputer-readable storage medium of claim 18, wherein the increasementvalue of the context is determined further based on the size of thecurrent video block, and wherein in response to a width-height ratio ofthe current video block being greater than 2, a context with a firstpredefined increasement value is used for coding the at least one bin ofthe syntax element, and in response to a width-height ratio of thecurrent video block being smaller than or equal to 2, a context with asecond increasement value is used for coding the at least one bin of thesyntax element, wherein the second increasement value is not identicalto the first predefined increasement value.
 20. A non-transitorycomputer-readable recording medium storing a bitstream of a video whichis generated by a method performed by a video processing apparatus,wherein the method comprises: determining whether a matrix intraprediction (MIP) mode is applied on a current video block of the videobased on a syntax element, wherein in the MIP mode, prediction samplesof the current video block are determined by performing a matrix vectormultiplication operation; and generating the bitstream based on thedetermining, wherein at least one bin of the syntax element is contextcoded, and an increasement value of the context is determined based oncharacteristics of a neighboring block of the current video block, andwherein a boundary down-sampling operation on reference samples of thecurrent video block and an up-sampling operation are included in the MIPmode based on a size of the current video block.